diff --git a/slither/core/declarations/contract.py b/slither/core/declarations/contract.py
index fd8f761c6..8e56120fe 100644
--- a/slither/core/declarations/contract.py
+++ b/slither/core/declarations/contract.py
@@ -93,6 +93,9 @@ class Contract(SourceMapping):  # pylint: disable=too-many-public-methods
         self._signatures: Optional[List[str]] = None
         self._signatures_declared: Optional[List[str]] = None
 
+        self._fallback_function: Optional["FunctionContract"] = None
+        self._receive_function: Optional["FunctionContract"] = None
+
         self._is_upgradeable: Optional[bool] = None
         self._is_upgradeable_proxy: Optional[bool] = None
         self._upgradeable_version: Optional[str] = None
@@ -663,6 +666,24 @@ class Contract(SourceMapping):  # pylint: disable=too-many-public-methods
         """
         return self.functions_declared + self.modifiers_declared  # type: ignore
 
+    @property
+    def fallback_function(self) -> Optional["FunctionContract"]:
+        if self._fallback_function is None:
+            for f in self.functions:
+                if f.is_fallback:
+                    self._fallback_function = f
+                    break
+        return self._fallback_function
+
+    @property
+    def receive_function(self) -> Optional["FunctionContract"]:
+        if self._receive_function is None:
+            for f in self.functions:
+                if f.is_receive:
+                    self._receive_function = f
+                    break
+        return self._receive_function
+
     def available_elements_from_inheritances(
         self,
         elements: Dict[str, "Function"],
diff --git a/slither/tools/upgradeability/checks/variables_order.py b/slither/tools/upgradeability/checks/variables_order.py
index fc83c44c6..002559b6e 100644
--- a/slither/tools/upgradeability/checks/variables_order.py
+++ b/slither/tools/upgradeability/checks/variables_order.py
@@ -6,6 +6,7 @@ from slither.tools.upgradeability.checks.abstract_checks import (
     AbstractCheck,
     CHECK_INFO,
 )
+from slither.utils.upgradeability import get_missing_vars
 from slither.utils.output import Output
 
 
@@ -55,25 +56,13 @@ Do not change the order of the state variables in the updated contract.
         contract2 = self.contract_v2
 
         assert contract2
-
-        order1 = [
-            variable
-            for variable in contract1.state_variables_ordered
-            if not (variable.is_constant or variable.is_immutable)
-        ]
-        order2 = [
-            variable
-            for variable in contract2.state_variables_ordered
-            if not (variable.is_constant or variable.is_immutable)
-        ]
+        missing = get_missing_vars(contract1, contract2)
 
         results = []
-        for idx, _ in enumerate(order1):
-            variable1 = order1[idx]
-            if len(order2) <= idx:
-                info: CHECK_INFO = ["Variable missing in ", contract2, ": ", variable1, "\n"]
-                json = self.generate_result(info)
-                results.append(json)
+        for variable1 in missing:
+            info: CHECK_INFO = ["Variable missing in ", contract2, ": ", variable1, "\n"]
+            json = self.generate_result(info)
+            results.append(json)
 
         return results
 
diff --git a/slither/utils/upgradeability.py b/slither/utils/upgradeability.py
new file mode 100644
index 000000000..7b4e8493a
--- /dev/null
+++ b/slither/utils/upgradeability.py
@@ -0,0 +1,580 @@
+from typing import Optional, Tuple, List, Union
+from slither.core.declarations import (
+    Contract,
+    Structure,
+    Enum,
+    SolidityVariableComposed,
+    SolidityVariable,
+    Function,
+)
+from slither.core.solidity_types import (
+    Type,
+    ElementaryType,
+    ArrayType,
+    MappingType,
+    UserDefinedType,
+)
+from slither.core.variables.local_variable import LocalVariable
+from slither.core.variables.local_variable_init_from_tuple import LocalVariableInitFromTuple
+from slither.core.variables.state_variable import StateVariable
+from slither.analyses.data_dependency.data_dependency import get_dependencies
+from slither.core.variables.variable import Variable
+from slither.core.expressions.literal import Literal
+from slither.core.expressions.identifier import Identifier
+from slither.core.expressions.call_expression import CallExpression
+from slither.core.expressions.assignment_operation import AssignmentOperation
+from slither.core.cfg.node import Node, NodeType
+from slither.slithir.operations import (
+    Operation,
+    Assignment,
+    Index,
+    Member,
+    Length,
+    Binary,
+    Unary,
+    Condition,
+    NewArray,
+    NewStructure,
+    NewContract,
+    NewElementaryType,
+    SolidityCall,
+    Delete,
+    EventCall,
+    LibraryCall,
+    InternalDynamicCall,
+    HighLevelCall,
+    LowLevelCall,
+    TypeConversion,
+    Return,
+    Transfer,
+    Send,
+    Unpack,
+    InitArray,
+    InternalCall,
+)
+from slither.slithir.variables import (
+    TemporaryVariable,
+    TupleVariable,
+    Constant,
+    ReferenceVariable,
+)
+from slither.tools.read_storage.read_storage import SlotInfo, SlitherReadStorage
+
+
+# pylint: disable=too-many-locals
+def compare(
+    v1: Contract, v2: Contract
+) -> Tuple[
+    List[Variable], List[Variable], List[Variable], List[Function], List[Function], List[Function]
+]:
+    """
+    Compares two versions of a contract. Most useful for upgradeable (logic) contracts,
+    but does not require that Contract.is_upgradeable returns true for either contract.
+
+    Args:
+        v1: Original version of (upgradeable) contract
+        v2: Updated version of (upgradeable) contract
+
+    Returns:
+        missing-vars-in-v2: list[Variable],
+        new-variables: list[Variable],
+        tainted-variables: list[Variable],
+        new-functions: list[Function],
+        modified-functions: list[Function],
+        tainted-functions: list[Function]
+    """
+
+    order_vars1 = [
+        v for v in v1.state_variables_ordered if not v.is_constant and not v.is_immutable
+    ]
+    order_vars2 = [
+        v for v in v2.state_variables_ordered if not v.is_constant and not v.is_immutable
+    ]
+    func_sigs1 = [function.solidity_signature for function in v1.functions]
+    func_sigs2 = [function.solidity_signature for function in v2.functions]
+
+    missing_vars_in_v2 = []
+    new_variables = []
+    tainted_variables = []
+    new_functions = []
+    modified_functions = []
+    tainted_functions = []
+
+    # Since this is not a detector, include any missing variables in the v2 contract
+    if len(order_vars2) < len(order_vars1):
+        missing_vars_in_v2.extend(get_missing_vars(v1, v2))
+
+    # Find all new and modified functions in the v2 contract
+    new_modified_functions = []
+    new_modified_function_vars = []
+    for sig in func_sigs2:
+        function = v2.get_function_from_signature(sig)
+        orig_function = v1.get_function_from_signature(sig)
+        if sig not in func_sigs1:
+            new_modified_functions.append(function)
+            new_functions.append(function)
+            new_modified_function_vars += (
+                function.state_variables_read + function.state_variables_written
+            )
+        elif not function.is_constructor_variables and is_function_modified(
+            orig_function, function
+        ):
+            new_modified_functions.append(function)
+            modified_functions.append(function)
+            new_modified_function_vars += (
+                function.state_variables_read + function.state_variables_written
+            )
+
+    # Find all unmodified functions that call a modified function or read/write the
+    # same state variable(s) as a new/modified function, i.e., tainted functions
+    for function in v2.functions:
+        if (
+            function in new_modified_functions
+            or function.is_constructor
+            or function.name.startswith("slither")
+        ):
+            continue
+        modified_calls = [
+            func for func in new_modified_functions if func in function.internal_calls
+        ]
+        tainted_vars = [
+            var
+            for var in set(new_modified_function_vars)
+            if var in function.variables_read_or_written
+            and not var.is_constant
+            and not var.is_immutable
+        ]
+        if len(modified_calls) > 0 or len(tainted_vars) > 0:
+            tainted_functions.append(function)
+
+    # Find all new or tainted variables, i.e., variables that are read or written by a new/modified/tainted function
+    for var in order_vars2:
+        read_by = v2.get_functions_reading_from_variable(var)
+        written_by = v2.get_functions_writing_to_variable(var)
+        if v1.get_state_variable_from_name(var.name) is None:
+            new_variables.append(var)
+        elif any(
+            func in read_by or func in written_by
+            for func in new_modified_functions + tainted_functions
+        ):
+            tainted_variables.append(var)
+
+    return (
+        missing_vars_in_v2,
+        new_variables,
+        tainted_variables,
+        new_functions,
+        modified_functions,
+        tainted_functions,
+    )
+
+
+def get_missing_vars(v1: Contract, v2: Contract) -> List[StateVariable]:
+    """
+    Gets all non-constant/immutable StateVariables that appear in v1 but not v2
+    Args:
+        v1: Contract version 1
+        v2: Contract version 2
+
+    Returns:
+        List of StateVariables from v1 missing in v2
+    """
+    results = []
+    order_vars1 = [
+        v for v in v1.state_variables_ordered if not v.is_constant and not v.is_immutable
+    ]
+    order_vars2 = [
+        v for v in v2.state_variables_ordered if not v.is_constant and not v.is_immutable
+    ]
+    if len(order_vars2) < len(order_vars1):
+        for variable in order_vars1:
+            if variable.name not in [v.name for v in order_vars2]:
+                results.append(variable)
+    return results
+
+
+def is_function_modified(f1: Function, f2: Function) -> bool:
+    """
+    Compares two versions of a function, and returns True if the function has been modified.
+    First checks whether the functions' content hashes are equal to quickly rule out identical functions.
+    Walks the CFGs and compares IR operations if hashes differ to rule out false positives, i.e., from changed comments.
+
+    Args:
+        f1: Original version of the function
+        f2: New version of the function
+
+    Returns:
+        True if the functions differ, otherwise False
+    """
+    # If the function content hashes are the same, no need to investigate the function further
+    if f1.source_mapping.content_hash == f2.source_mapping.content_hash:
+        return False
+    # If the hashes differ, it is possible a change in a name or in a comment could be the only difference
+    # So we need to resort to walking through the CFG and comparing the IR operations
+    queue_f1 = [f1.entry_point]
+    queue_f2 = [f2.entry_point]
+    visited = []
+    while len(queue_f1) > 0 and len(queue_f2) > 0:
+        node_f1 = queue_f1.pop(0)
+        node_f2 = queue_f2.pop(0)
+        visited.extend([node_f1, node_f2])
+        queue_f1.extend(son for son in node_f1.sons if son not in visited)
+        queue_f2.extend(son for son in node_f2.sons if son not in visited)
+        for i, ir in enumerate(node_f1.irs):
+            if encode_ir_for_compare(ir) != encode_ir_for_compare(node_f2.irs[i]):
+                return True
+    return False
+
+
+# pylint: disable=too-many-branches
+def ntype(_type: Union[Type, str]) -> str:
+    if isinstance(_type, ElementaryType):
+        _type = str(_type)
+    elif isinstance(_type, ArrayType):
+        if isinstance(_type.type, ElementaryType):
+            _type = str(_type)
+        else:
+            _type = "user_defined_array"
+    elif isinstance(_type, Structure):
+        _type = str(_type)
+    elif isinstance(_type, Enum):
+        _type = str(_type)
+    elif isinstance(_type, MappingType):
+        _type = str(_type)
+    elif isinstance(_type, UserDefinedType):
+        if isinstance(_type.type, Contract):
+            _type = f"contract({_type.type.name})"
+        elif isinstance(_type.type, Structure):
+            _type = f"struct({_type.type.name})"
+        elif isinstance(_type.type, Enum):
+            _type = f"enum({_type.type.name})"
+    else:
+        _type = str(_type)
+
+    _type = _type.replace(" memory", "")
+    _type = _type.replace(" storage ref", "")
+
+    if "struct" in _type:
+        return "struct"
+    if "enum" in _type:
+        return "enum"
+    if "tuple" in _type:
+        return "tuple"
+    if "contract" in _type:
+        return "contract"
+    if "mapping" in _type:
+        return "mapping"
+    return _type.replace(" ", "_")
+
+
+# pylint: disable=too-many-branches
+def encode_ir_for_compare(ir: Operation) -> str:
+    # operations
+    if isinstance(ir, Assignment):
+        return f"({encode_var_for_compare(ir.lvalue)}):=({encode_var_for_compare(ir.rvalue)})"
+    if isinstance(ir, Index):
+        return f"index({ntype(ir.index_type)})"
+    if isinstance(ir, Member):
+        return "member"  # .format(ntype(ir._type))
+    if isinstance(ir, Length):
+        return "length"
+    if isinstance(ir, Binary):
+        return f"binary({str(ir.variable_left)}{str(ir.type)}{str(ir.variable_right)})"
+    if isinstance(ir, Unary):
+        return f"unary({str(ir.type)})"
+    if isinstance(ir, Condition):
+        return f"condition({encode_var_for_compare(ir.value)})"
+    if isinstance(ir, NewStructure):
+        return "new_structure"
+    if isinstance(ir, NewContract):
+        return "new_contract"
+    if isinstance(ir, NewArray):
+        return f"new_array({ntype(ir.array_type)})"
+    if isinstance(ir, NewElementaryType):
+        return f"new_elementary({ntype(ir.type)})"
+    if isinstance(ir, Delete):
+        return f"delete({encode_var_for_compare(ir.lvalue)},{encode_var_for_compare(ir.variable)})"
+    if isinstance(ir, SolidityCall):
+        return f"solidity_call({ir.function.full_name})"
+    if isinstance(ir, InternalCall):
+        return f"internal_call({ntype(ir.type_call)})"
+    if isinstance(ir, EventCall):  # is this useful?
+        return "event"
+    if isinstance(ir, LibraryCall):
+        return "library_call"
+    if isinstance(ir, InternalDynamicCall):
+        return "internal_dynamic_call"
+    if isinstance(ir, HighLevelCall):  # TODO: improve
+        return "high_level_call"
+    if isinstance(ir, LowLevelCall):  # TODO: improve
+        return "low_level_call"
+    if isinstance(ir, TypeConversion):
+        return f"type_conversion({ntype(ir.type)})"
+    if isinstance(ir, Return):  # this can be improved using values
+        return "return"  # .format(ntype(ir.type))
+    if isinstance(ir, Transfer):
+        return f"transfer({encode_var_for_compare(ir.call_value)})"
+    if isinstance(ir, Send):
+        return f"send({encode_var_for_compare(ir.call_value)})"
+    if isinstance(ir, Unpack):  # TODO: improve
+        return "unpack"
+    if isinstance(ir, InitArray):  # TODO: improve
+        return "init_array"
+
+    # default
+    return ""
+
+
+# pylint: disable=too-many-branches
+def encode_var_for_compare(var: Variable) -> str:
+
+    # variables
+    if isinstance(var, Constant):
+        return f"constant({ntype(var.type)})"
+    if isinstance(var, SolidityVariableComposed):
+        return f"solidity_variable_composed({var.name})"
+    if isinstance(var, SolidityVariable):
+        return f"solidity_variable{var.name}"
+    if isinstance(var, TemporaryVariable):
+        return "temporary_variable"
+    if isinstance(var, ReferenceVariable):
+        return f"reference({ntype(var.type)})"
+    if isinstance(var, LocalVariable):
+        return f"local_solc_variable({var.location})"
+    if isinstance(var, StateVariable):
+        return f"state_solc_variable({ntype(var.type)})"
+    if isinstance(var, LocalVariableInitFromTuple):
+        return "local_variable_init_tuple"
+    if isinstance(var, TupleVariable):
+        return "tuple_variable"
+
+    # default
+    return ""
+
+
+def get_proxy_implementation_slot(proxy: Contract) -> Optional[SlotInfo]:
+    """
+    Gets information about the storage slot where a proxy's implementation address is stored.
+    Args:
+        proxy: A Contract object (proxy.is_upgradeable_proxy should be true).
+
+    Returns:
+        (`SlotInfo`) | None : A dictionary of the slot information.
+    """
+
+    delegate = get_proxy_implementation_var(proxy)
+    if isinstance(delegate, StateVariable):
+        if not delegate.is_constant and not delegate.is_immutable:
+            srs = SlitherReadStorage([proxy], 20)
+            return srs.get_storage_slot(delegate, proxy)
+        if delegate.is_constant and delegate.type.name == "bytes32":
+            return SlotInfo(
+                name=delegate.name,
+                type_string="address",
+                slot=int(delegate.expression.value, 16),
+                size=160,
+                offset=0,
+            )
+    return None
+
+
+def get_proxy_implementation_var(proxy: Contract) -> Optional[Variable]:
+    """
+    Gets the Variable that stores a proxy's implementation address. Uses data dependency to trace any LocalVariable
+    that is passed into a delegatecall as the target address back to its data source, ideally a StateVariable.
+    Can return a newly created StateVariable if an `sload` from a hardcoded storage slot is found in assembly.
+    Args:
+        proxy: A Contract object (proxy.is_upgradeable_proxy should be true).
+
+    Returns:
+        (`Variable`) | None : The variable, ideally a StateVariable, which stores the proxy's implementation address.
+    """
+    if not proxy.is_upgradeable_proxy or not proxy.fallback_function:
+        return None
+
+    delegate = find_delegate_in_fallback(proxy)
+    if isinstance(delegate, LocalVariable):
+        dependencies = get_dependencies(delegate, proxy)
+        try:
+            delegate = next(var for var in dependencies if isinstance(var, StateVariable))
+        except StopIteration:
+            return delegate
+    return delegate
+
+
+def find_delegate_in_fallback(proxy: Contract) -> Optional[Variable]:
+    """
+    Searches a proxy's fallback function for a delegatecall, then extracts the Variable being passed in as the target.
+    Can return a newly created StateVariable if an `sload` from a hardcoded storage slot is found in assembly.
+    Should typically be called by get_proxy_implementation_var(proxy).
+    Args:
+        proxy: A Contract object (should have a fallback function).
+
+    Returns:
+        (`Variable`) | None : The variable being passed as the destination argument in a delegatecall in the fallback.
+    """
+    delegate: Optional[Variable] = None
+    fallback = proxy.fallback_function
+    for node in fallback.all_nodes():
+        for ir in node.irs:
+            if isinstance(ir, LowLevelCall) and ir.function_name == "delegatecall":
+                delegate = ir.destination
+        if delegate is not None:
+            break
+        if (
+            node.type == NodeType.ASSEMBLY
+            and isinstance(node.inline_asm, str)
+            and "delegatecall" in node.inline_asm
+        ):
+            delegate = extract_delegate_from_asm(proxy, node)
+        elif node.type == NodeType.EXPRESSION:
+            expression = node.expression
+            if isinstance(expression, AssignmentOperation):
+                expression = expression.expression_right
+            if (
+                isinstance(expression, CallExpression)
+                and "delegatecall" in str(expression.called)
+                and len(expression.arguments) > 1
+            ):
+                dest = expression.arguments[1]
+                if isinstance(dest, CallExpression) and "sload" in str(dest.called):
+                    dest = dest.arguments[0]
+                if isinstance(dest, Identifier):
+                    delegate = dest.value
+                    break
+                if (
+                    isinstance(dest, Literal) and len(dest.value) == 66
+                ):  # 32 bytes = 64 chars + "0x" = 66 chars
+                    # Storage slot is not declared as a constant, but rather is hardcoded in the assembly,
+                    # so create a new StateVariable to represent it.
+                    delegate = create_state_variable_from_slot(dest.value)
+                    break
+    return delegate
+
+
+def extract_delegate_from_asm(contract: Contract, node: Node) -> Optional[Variable]:
+    """
+    Finds a Variable with a name matching the argument passed into a delegatecall, when all we have is an Assembly node
+    with a block of code as one long string. Usually only the case for solc versions < 0.6.0.
+    Can return a newly created StateVariable if an `sload` from a hardcoded storage slot is found in assembly.
+    Should typically be called by find_delegate_in_fallback(proxy).
+    Args:
+        contract: The parent Contract.
+        node: The Assembly Node (i.e., node.type == NodeType.ASSEMBLY)
+
+    Returns:
+        (`Variable`) | None : The variable being passed as the destination argument in a delegatecall in the fallback.
+    """
+    asm_split = str(node.inline_asm).split("\n")
+    asm = next(line for line in asm_split if "delegatecall" in line)
+    params = asm.split("call(")[1].split(", ")
+    dest = params[1]
+    if dest.endswith(")") and not dest.startswith("sload("):
+        dest = params[2]
+    if dest.startswith("sload("):
+        dest = dest.replace(")", "(").split("(")[1]
+        if dest.startswith("0x"):
+            return create_state_variable_from_slot(dest)
+        if dest.isnumeric():
+            slot_idx = int(dest)
+            return next(
+                (
+                    v
+                    for v in contract.state_variables_ordered
+                    if SlitherReadStorage.get_variable_info(contract, v)[0] == slot_idx
+                ),
+                None,
+            )
+        for v in node.function.variables_read_or_written:
+            if v.name == dest:
+                if isinstance(v, LocalVariable) and v.expression is not None:
+                    e = v.expression
+                    if isinstance(e, Identifier) and isinstance(e.value, StateVariable):
+                        v = e.value
+                        # Fall through, return constant storage slot
+                if isinstance(v, StateVariable) and v.is_constant:
+                    return v
+    if "_fallback_asm" in dest or "_slot" in dest:
+        dest = dest.split("_")[0]
+    return find_delegate_from_name(contract, dest, node.function)
+
+
+def find_delegate_from_name(
+    contract: Contract, dest: str, parent_func: Function
+) -> Optional[Variable]:
+    """
+    Searches for a variable with a given name, starting with StateVariables declared in the contract, followed by
+    LocalVariables in the parent function, either declared in the function body or as parameters in the signature.
+    Can return a newly created StateVariable if an `sload` from a hardcoded storage slot is found in assembly.
+    Args:
+        contract: The Contract object to search.
+        dest: The variable name to search for.
+        parent_func: The Function object to search.
+
+    Returns:
+        (`Variable`) | None : The variable with the matching name, if found
+    """
+    for sv in contract.state_variables:
+        if sv.name == dest:
+            return sv
+    for lv in parent_func.local_variables:
+        if lv.name == dest:
+            return lv
+    for pv in parent_func.parameters + parent_func.returns:
+        if pv.name == dest:
+            return pv
+    if parent_func.contains_assembly:
+        for node in parent_func.all_nodes():
+            if node.type == NodeType.ASSEMBLY and isinstance(node.inline_asm, str):
+                asm = next(
+                    (
+                        s
+                        for s in node.inline_asm.split("\n")
+                        if f"{dest}:=sload(" in s.replace(" ", "")
+                    ),
+                    None,
+                )
+                if asm:
+                    slot = asm.split("sload(")[1].split(")")[0]
+                    if slot.startswith("0x"):
+                        return create_state_variable_from_slot(slot, name=dest)
+                    try:
+                        slot_idx = int(slot)
+                        return next(
+                            (
+                                v
+                                for v in contract.state_variables_ordered
+                                if SlitherReadStorage.get_variable_info(contract, v)[0] == slot_idx
+                            ),
+                            None,
+                        )
+                    except TypeError:
+                        continue
+    return None
+
+
+def create_state_variable_from_slot(slot: str, name: str = None) -> Optional[StateVariable]:
+    """
+    Creates a new StateVariable object to wrap a hardcoded storage slot found in assembly.
+    Args:
+        slot: The storage slot hex string.
+        name: Optional name for the variable. The slot string is used if name is not provided.
+
+    Returns:
+        A newly created constant StateVariable of type bytes32, with the slot as the variable's expression and name,
+        if slot matches the length and prefix of a bytes32. Otherwise, returns None.
+    """
+    if len(slot) == 66 and slot.startswith("0x"):  # 32 bytes = 64 chars + "0x" = 66 chars
+        # Storage slot is not declared as a constant, but rather is hardcoded in the assembly,
+        # so create a new StateVariable to represent it.
+        v = StateVariable()
+        v.is_constant = True
+        v.expression = Literal(slot, ElementaryType("bytes32"))
+        if name is not None:
+            v.name = name
+        else:
+            v.name = slot
+        v.type = ElementaryType("bytes32")
+        return v
+    # This should probably also handle hashed strings, but for now return None
+    return None
diff --git a/tests/unit/core/test_data/fallback.sol b/tests/unit/core/test_data/fallback.sol
new file mode 100644
index 000000000..cd7dc1812
--- /dev/null
+++ b/tests/unit/core/test_data/fallback.sol
@@ -0,0 +1,29 @@
+pragma solidity ^0.6.12;
+
+contract FakeFallback {
+    mapping(address => uint) public contributions;
+    address payable public owner;
+
+    constructor() public {
+        owner = payable(msg.sender);
+        contributions[msg.sender] = 1000 * (1 ether);
+    }
+
+    function fallback() public payable {
+        contributions[msg.sender] += msg.value;
+    }
+
+    function receive() public payable {
+        contributions[msg.sender] += msg.value;
+    }
+}
+
+contract Fallback is FakeFallback {
+    receive() external payable {
+        contributions[msg.sender] += msg.value;
+    }
+
+    fallback() external payable {
+        contributions[msg.sender] += msg.value;
+    }
+}
diff --git a/tests/unit/core/test_fallback_receive.py b/tests/unit/core/test_fallback_receive.py
new file mode 100644
index 000000000..505a9dd6f
--- /dev/null
+++ b/tests/unit/core/test_fallback_receive.py
@@ -0,0 +1,20 @@
+from pathlib import Path
+from solc_select import solc_select
+
+from slither import Slither
+from slither.core.declarations.function import FunctionType
+
+TEST_DATA_DIR = Path(__file__).resolve().parent / "test_data"
+
+
+def test_fallback_receive():
+    solc_select.switch_global_version("0.6.12", always_install=True)
+    file = Path(TEST_DATA_DIR, "fallback.sol").as_posix()
+    slither = Slither(file)
+    fake_fallback = slither.get_contract_from_name("FakeFallback")[0]
+    real_fallback = slither.get_contract_from_name("Fallback")[0]
+
+    assert fake_fallback.fallback_function is None
+    assert fake_fallback.receive_function is None
+    assert real_fallback.fallback_function.function_type == FunctionType.FALLBACK
+    assert real_fallback.receive_function.function_type == FunctionType.RECEIVE
diff --git a/tests/unit/utils/test_data/upgradeability_util/TestUpgrades-0.5.0.sol b/tests/unit/utils/test_data/upgradeability_util/TestUpgrades-0.5.0.sol
new file mode 100644
index 000000000..eaecfa6e9
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/TestUpgrades-0.5.0.sol
@@ -0,0 +1,6 @@
+pragma solidity ^0.5.0;
+
+import "./src/EIP1822Proxy.sol";
+import "./src/ZosProxy.sol";
+import "./src/MasterCopyProxy.sol";
+import "./src/SynthProxy.sol";
diff --git a/tests/unit/utils/test_data/upgradeability_util/TestUpgrades-0.8.2.sol b/tests/unit/utils/test_data/upgradeability_util/TestUpgrades-0.8.2.sol
new file mode 100644
index 000000000..d3371d3c6
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/TestUpgrades-0.8.2.sol
@@ -0,0 +1,6 @@
+pragma solidity ^0.8.2;
+
+import "./src/ContractV1.sol";
+import "./src/ContractV2.sol";
+import "./src/InheritedStorageProxy.sol";
+import "./src/ERC1967Proxy.sol";
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/Address.sol b/tests/unit/utils/test_data/upgradeability_util/src/Address.sol
new file mode 100644
index 000000000..d440b259e
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/Address.sol
@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (last updated v4.8.0) (utils/Address.sol)
+
+pragma solidity ^0.8.1;
+
+/**
+ * @dev Collection of functions related to the address type
+ */
+library Address {
+    /**
+     * @dev Returns true if `account` is a contract.
+     *
+     * [IMPORTANT]
+     * ====
+     * It is unsafe to assume that an address for which this function returns
+     * false is an externally-owned account (EOA) and not a contract.
+     *
+     * Among others, `isContract` will return false for the following
+     * types of addresses:
+     *
+     *  - an externally-owned account
+     *  - a contract in construction
+     *  - an address where a contract will be created
+     *  - an address where a contract lived, but was destroyed
+     * ====
+     *
+     * [IMPORTANT]
+     * ====
+     * You shouldn't rely on `isContract` to protect against flash loan attacks!
+     *
+     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
+     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
+     * constructor.
+     * ====
+     */
+    function isContract(address account) internal view returns (bool) {
+        // This method relies on extcodesize/address.code.length, which returns 0
+        // for contracts in construction, since the code is only stored at the end
+        // of the constructor execution.
+
+        return account.code.length > 0;
+    }
+
+    /**
+     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
+     * `recipient`, forwarding all available gas and reverting on errors.
+     *
+     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
+     * of certain opcodes, possibly making contracts go over the 2300 gas limit
+     * imposed by `transfer`, making them unable to receive funds via
+     * `transfer`. {sendValue} removes this limitation.
+     *
+     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
+     *
+     * IMPORTANT: because control is transferred to `recipient`, care must be
+     * taken to not create reentrancy vulnerabilities. Consider using
+     * {ReentrancyGuard} or the
+     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
+     */
+    function sendValue(address payable recipient, uint256 amount) internal {
+        require(address(this).balance >= amount, "Address: insufficient balance");
+
+        (bool success, ) = recipient.call{value: amount}("");
+        require(success, "Address: unable to send value, recipient may have reverted");
+    }
+
+    /**
+     * @dev Performs a Solidity function call using a low level `call`. A
+     * plain `call` is an unsafe replacement for a function call: use this
+     * function instead.
+     *
+     * If `target` reverts with a revert reason, it is bubbled up by this
+     * function (like regular Solidity function calls).
+     *
+     * Returns the raw returned data. To convert to the expected return value,
+     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
+     *
+     * Requirements:
+     *
+     * - `target` must be a contract.
+     * - calling `target` with `data` must not revert.
+     *
+     * _Available since v3.1._
+     */
+    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
+        return functionCallWithValue(target, data, 0, "Address: low-level call failed");
+    }
+
+    /**
+     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
+     * `errorMessage` as a fallback revert reason when `target` reverts.
+     *
+     * _Available since v3.1._
+     */
+    function functionCall(
+        address target,
+        bytes memory data,
+        string memory errorMessage
+    ) internal returns (bytes memory) {
+        return functionCallWithValue(target, data, 0, errorMessage);
+    }
+
+    /**
+     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
+     * but also transferring `value` wei to `target`.
+     *
+     * Requirements:
+     *
+     * - the calling contract must have an ETH balance of at least `value`.
+     * - the called Solidity function must be `payable`.
+     *
+     * _Available since v3.1._
+     */
+    function functionCallWithValue(
+        address target,
+        bytes memory data,
+        uint256 value
+    ) internal returns (bytes memory) {
+        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
+    }
+
+    /**
+     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
+     * with `errorMessage` as a fallback revert reason when `target` reverts.
+     *
+     * _Available since v3.1._
+     */
+    function functionCallWithValue(
+        address target,
+        bytes memory data,
+        uint256 value,
+        string memory errorMessage
+    ) internal returns (bytes memory) {
+        require(address(this).balance >= value, "Address: insufficient balance for call");
+        (bool success, bytes memory returndata) = target.call{value: value}(data);
+        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
+    }
+
+    /**
+     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
+     * but performing a static call.
+     *
+     * _Available since v3.3._
+     */
+    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
+        return functionStaticCall(target, data, "Address: low-level static call failed");
+    }
+
+    /**
+     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
+     * but performing a static call.
+     *
+     * _Available since v3.3._
+     */
+    function functionStaticCall(
+        address target,
+        bytes memory data,
+        string memory errorMessage
+    ) internal view returns (bytes memory) {
+        (bool success, bytes memory returndata) = target.staticcall(data);
+        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
+    }
+
+    /**
+     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
+     * but performing a delegate call.
+     *
+     * _Available since v3.4._
+     */
+    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
+        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
+    }
+
+    /**
+     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
+     * but performing a delegate call.
+     *
+     * _Available since v3.4._
+     */
+    function functionDelegateCall(
+        address target,
+        bytes memory data,
+        string memory errorMessage
+    ) internal returns (bytes memory) {
+        (bool success, bytes memory returndata) = target.delegatecall(data);
+        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
+    }
+
+    /**
+     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
+     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
+     *
+     * _Available since v4.8._
+     */
+    function verifyCallResultFromTarget(
+        address target,
+        bool success,
+        bytes memory returndata,
+        string memory errorMessage
+    ) internal view returns (bytes memory) {
+        if (success) {
+            if (returndata.length == 0) {
+                // only check isContract if the call was successful and the return data is empty
+                // otherwise we already know that it was a contract
+                require(isContract(target), "Address: call to non-contract");
+            }
+            return returndata;
+        } else {
+            _revert(returndata, errorMessage);
+        }
+    }
+
+    /**
+     * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
+     * revert reason or using the provided one.
+     *
+     * _Available since v4.3._
+     */
+    function verifyCallResult(
+        bool success,
+        bytes memory returndata,
+        string memory errorMessage
+    ) internal pure returns (bytes memory) {
+        if (success) {
+            return returndata;
+        } else {
+            _revert(returndata, errorMessage);
+        }
+    }
+
+    function _revert(bytes memory returndata, string memory errorMessage) private pure {
+        // Look for revert reason and bubble it up if present
+        if (returndata.length > 0) {
+            // The easiest way to bubble the revert reason is using memory via assembly
+            /// @solidity memory-safe-assembly
+            assembly {
+                let returndata_size := mload(returndata)
+                revert(add(32, returndata), returndata_size)
+            }
+        } else {
+            revert(errorMessage);
+        }
+    }
+}
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/ContractV1.sol b/tests/unit/utils/test_data/upgradeability_util/src/ContractV1.sol
new file mode 100644
index 000000000..1e2c4b476
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/ContractV1.sol
@@ -0,0 +1,36 @@
+pragma solidity ^0.8.2;
+
+import "./ProxyStorage.sol";
+
+contract ContractV1 is ProxyStorage {
+    uint private stateA = 0;
+    uint private stateB = 0;
+    uint constant CONST = 32;
+    bool bug = false;
+
+    function f(uint x) public {
+        if (msg.sender == admin) {
+            stateA = x;
+        }
+    }
+
+    function g(uint y) public {
+        if (checkA()) {
+            stateB = y - 10;
+        }
+    }
+
+    function h() public {
+        if (checkB()) {
+            bug = true;
+        }
+    }
+
+    function checkA() internal returns (bool) {
+        return stateA % CONST == 1;
+    }
+
+    function checkB() internal returns (bool) {
+        return stateB == 62;
+    }
+}
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/ContractV2.sol b/tests/unit/utils/test_data/upgradeability_util/src/ContractV2.sol
new file mode 100644
index 000000000..9b102f3e9
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/ContractV2.sol
@@ -0,0 +1,41 @@
+pragma solidity ^0.8.2;
+
+import "./ProxyStorage.sol";
+
+contract ContractV2 is ProxyStorage {
+    uint private stateA = 0;
+    uint private stateB = 0;
+    uint constant CONST = 32;
+    bool bug = false;
+    uint private stateC = 0;
+
+    function f(uint x) public {
+        if (msg.sender == admin) {
+            stateA = x;
+        }
+    }
+
+    function g(uint y) public {
+        if (checkA()) {
+            stateB = y - 10;
+        }
+    }
+
+    function h() public {
+        if (checkB()) {
+            bug = true;
+        }
+    }
+
+    function i() public {
+        stateC = stateC + 1;
+    }
+
+    function checkA() internal returns (bool) {
+        return stateA % CONST == 1;
+    }
+
+    function checkB() internal returns (bool) {
+        return stateB == 32;
+    }
+}
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/EIP1822Proxy.sol b/tests/unit/utils/test_data/upgradeability_util/src/EIP1822Proxy.sol
new file mode 100644
index 000000000..3145eb17e
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/EIP1822Proxy.sol
@@ -0,0 +1,47 @@
+pragma solidity ^0.5.0;
+
+contract EIP1822Proxy {
+    // Code position in storage is keccak256("PROXIABLE") = "0xc5f16f0fcc639fa48a6947836d9850f504798523bf8c9a3a87d5876cf622bcf7"
+    constructor(bytes memory constructData, address contractLogic) public {
+        // save the code address
+        assembly { // solium-disable-line
+            sstore(0xc5f16f0fcc639fa48a6947836d9850f504798523bf8c9a3a87d5876cf622bcf7, contractLogic)
+        }
+        (bool success, bytes memory _ ) = contractLogic.delegatecall(constructData); // solium-disable-line
+        require(success, "Construction failed");
+    }
+
+    function() external payable {
+        assembly { // solium-disable-line
+            let contractLogic := sload(0xc5f16f0fcc639fa48a6947836d9850f504798523bf8c9a3a87d5876cf622bcf7)
+            calldatacopy(0x0, 0x0, calldatasize)
+            let success := delegatecall(sub(gas, 10000), contractLogic, 0x0, calldatasize, 0, 0)
+            let retSz := returndatasize
+            returndatacopy(0, 0, retSz)
+            switch success
+            case 0 {
+                revert(0, retSz)
+            }
+            default {
+                return(0, retSz)
+            }
+        }
+    }
+}
+
+contract EIP1822Proxiable {
+    // Code position in storage is keccak256("PROXIABLE") = "0xc5f16f0fcc639fa48a6947836d9850f504798523bf8c9a3a87d5876cf622bcf7"
+
+    function updateCodeAddress(address newAddress) internal {
+        require(
+            bytes32(0xc5f16f0fcc639fa48a6947836d9850f504798523bf8c9a3a87d5876cf622bcf7) == EIP1822Proxiable(newAddress).proxiableUUID(),
+            "Not compatible"
+        );
+        assembly { // solium-disable-line
+            sstore(0xc5f16f0fcc639fa48a6947836d9850f504798523bf8c9a3a87d5876cf622bcf7, newAddress)
+        }
+    }
+    function proxiableUUID() public pure returns (bytes32) {
+        return 0xc5f16f0fcc639fa48a6947836d9850f504798523bf8c9a3a87d5876cf622bcf7;
+    }
+}
\ No newline at end of file
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/ERC1967Proxy.sol b/tests/unit/utils/test_data/upgradeability_util/src/ERC1967Proxy.sol
new file mode 100644
index 000000000..f1496c27e
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/ERC1967Proxy.sol
@@ -0,0 +1,15 @@
+pragma solidity ^0.8.0;
+
+import "./Proxy.sol";
+import "./ERC1967Upgrade.sol";
+
+contract ERC1967Proxy is Proxy, ERC1967Upgrade {
+
+    constructor(address _logic, bytes memory _data) payable {
+        _upgradeToAndCall(_logic, _data, false);
+    }
+
+    function _implementation() internal view virtual override returns (address impl) {
+        return ERC1967Upgrade._getImplementation();
+    }
+}
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/ERC1967Upgrade.sol b/tests/unit/utils/test_data/upgradeability_util/src/ERC1967Upgrade.sol
new file mode 100644
index 000000000..d089e94d9
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/ERC1967Upgrade.sol
@@ -0,0 +1,105 @@
+pragma solidity ^0.8.2;
+
+import "./Address.sol";
+import "./StorageSlot.sol";
+
+interface IBeacon {
+    function implementation() external view returns (address);
+}
+
+interface IERC1822Proxiable {
+    function proxiableUUID() external view returns (bytes32);
+}
+
+abstract contract ERC1967Upgrade {
+
+    bytes32 private constant _ROLLBACK_SLOT = 0x4910fdfa16fed3260ed0e7147f7cc6da11a60208b5b9406d12a635614ffd9143;
+    bytes32 internal constant _IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;
+    bytes32 internal constant _ADMIN_SLOT = 0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103;
+    bytes32 internal constant _BEACON_SLOT = 0xa3f0ad74e5423aebfd80d3ef4346578335a9a72aeaee59ff6cb3582b35133d50;
+
+    event Upgraded(address indexed implementation);
+    event AdminChanged(address previousAdmin, address newAdmin);
+    event BeaconUpgraded(address indexed beacon);
+
+    function _getImplementation() internal view returns (address) {
+        return StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value;
+    }
+
+    function _setImplementation(address newImplementation) private {
+        require(Address.isContract(newImplementation), "ERC1967: new implementation is not a contract");
+        StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value = newImplementation;
+    }
+
+    function _upgradeTo(address newImplementation) internal {
+        _setImplementation(newImplementation);
+        emit Upgraded(newImplementation);
+    }
+
+    function _upgradeToAndCall(
+        address newImplementation,
+        bytes memory data,
+        bool forceCall
+    ) internal {
+        _upgradeTo(newImplementation);
+        if (data.length > 0 || forceCall) {
+            Address.functionDelegateCall(newImplementation, data);
+        }
+    }
+
+    function _upgradeToAndCallUUPS(
+        address newImplementation,
+        bytes memory data,
+        bool forceCall
+    ) internal {
+        if (StorageSlot.getBooleanSlot(_ROLLBACK_SLOT).value) {
+            _setImplementation(newImplementation);
+        } else {
+            try IERC1822Proxiable(newImplementation).proxiableUUID() returns (bytes32 slot) {
+                require(slot == _IMPLEMENTATION_SLOT, "ERC1967Upgrade: unsupported proxiableUUID");
+            } catch {
+                revert("ERC1967Upgrade: new implementation is not UUPS");
+            }
+            _upgradeToAndCall(newImplementation, data, forceCall);
+        }
+    }
+
+    function _getAdmin() internal view returns (address) {
+        return StorageSlot.getAddressSlot(_ADMIN_SLOT).value;
+    }
+
+    function _setAdmin(address newAdmin) private {
+        require(newAdmin != address(0), "ERC1967: new admin is the zero address");
+        StorageSlot.getAddressSlot(_ADMIN_SLOT).value = newAdmin;
+    }
+
+    function _changeAdmin(address newAdmin) internal {
+        emit AdminChanged(_getAdmin(), newAdmin);
+        _setAdmin(newAdmin);
+    }
+
+    function _getBeacon() internal view returns (address) {
+        return StorageSlot.getAddressSlot(_BEACON_SLOT).value;
+    }
+
+    function _setBeacon(address newBeacon) private {
+        require(Address.isContract(newBeacon), "ERC1967: new beacon is not a contract");
+        require(
+            Address.isContract(IBeacon(newBeacon).implementation()),
+            "ERC1967: beacon implementation is not a contract"
+        );
+        StorageSlot.getAddressSlot(_BEACON_SLOT).value = newBeacon;
+    }
+
+    function _upgradeBeaconToAndCall(
+        address newBeacon,
+        bytes memory data,
+        bool forceCall
+    ) internal {
+        _setBeacon(newBeacon);
+        emit BeaconUpgraded(newBeacon);
+        if (data.length > 0 || forceCall) {
+            Address.functionDelegateCall(IBeacon(newBeacon).implementation(), data);
+        }
+    }
+}
\ No newline at end of file
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/InheritedStorageProxy.sol b/tests/unit/utils/test_data/upgradeability_util/src/InheritedStorageProxy.sol
new file mode 100644
index 000000000..eddbfb0f1
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/InheritedStorageProxy.sol
@@ -0,0 +1,39 @@
+pragma solidity ^0.8.0;
+
+import "./Proxy.sol";
+import "./ProxyStorage.sol";
+
+contract InheritedStorageProxy is Proxy, ProxyStorage {
+    constructor(address _implementation) {
+        admin = msg.sender;
+        implementation = _implementation;
+    }
+
+    function getImplementation() external view returns (address) {
+        return _implementation();
+    }
+
+    function getAdmin() external view returns (address) {
+        return _admin();
+    }
+
+    function upgrade(address _newImplementation) external {
+        require(msg.sender == admin, "Only admin can upgrade");
+        implementation = _newImplementation;
+    }
+
+    function setAdmin(address _newAdmin) external {
+        require(msg.sender == admin, "Only current admin can change admin");
+        admin = _newAdmin;
+    }
+
+    function _implementation() internal view override returns (address) {
+        return implementation;
+    }
+
+    function _admin() internal view returns (address) {
+        return admin;
+    }
+
+    function _beforeFallback() internal override {}
+}
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/MasterCopyProxy.sol b/tests/unit/utils/test_data/upgradeability_util/src/MasterCopyProxy.sol
new file mode 100644
index 000000000..d25a2a920
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/MasterCopyProxy.sol
@@ -0,0 +1,27 @@
+pragma solidity ^0.5.0;
+
+contract MasterCopyProxy {
+    address internal masterCopy;
+
+    constructor(address _masterCopy)
+        public
+    {
+        require(_masterCopy != address(0), "Invalid master copy address provided");
+        masterCopy = _masterCopy;
+    }
+
+    /// @dev Fallback function forwards all transactions and returns all received return data.
+    function ()
+        external
+        payable
+    {
+        // solium-disable-next-line security/no-inline-assembly
+        assembly {
+            calldatacopy(0, 0, calldatasize())
+            let success := delegatecall(gas, sload(0), 0, calldatasize(), 0, 0)
+            returndatacopy(0, 0, returndatasize())
+            if eq(success, 0) { revert(0, returndatasize()) }
+            return(0, returndatasize())
+        }
+    }
+}
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/Proxy.sol b/tests/unit/utils/test_data/upgradeability_util/src/Proxy.sol
new file mode 100644
index 000000000..445ddb170
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/Proxy.sol
@@ -0,0 +1,36 @@
+pragma solidity ^0.8.0;
+
+abstract contract Proxy {
+
+    function _delegate(address implementation) internal virtual {
+        assembly {
+            calldatacopy(0, 0, calldatasize())
+            let result := delegatecall(gas(), implementation, 0, calldatasize(), 0, 0)
+            returndatacopy(0, 0, returndatasize())
+            switch result
+            case 0 {
+                revert(0, returndatasize())
+            }
+            default {
+                return(0, returndatasize())
+            }
+        }
+    }
+
+    function _implementation() internal view virtual returns (address);
+
+    function _fallback() internal virtual {
+        _beforeFallback();
+        _delegate(_implementation());
+    }
+
+    fallback() external payable virtual {
+        _fallback();
+    }
+
+    receive() external payable virtual {
+        _fallback();
+    }
+
+    function _beforeFallback() internal virtual {}
+}
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/ProxyStorage.sol b/tests/unit/utils/test_data/upgradeability_util/src/ProxyStorage.sol
new file mode 100644
index 000000000..d591040bd
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/ProxyStorage.sol
@@ -0,0 +1,6 @@
+pragma solidity ^0.8.0;
+
+contract ProxyStorage {
+    address internal admin;
+    address internal implementation;
+}
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/StorageSlot.sol b/tests/unit/utils/test_data/upgradeability_util/src/StorageSlot.sol
new file mode 100644
index 000000000..6ab8f5dc6
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/StorageSlot.sol
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (last updated v4.7.0) (utils/StorageSlot.sol)
+
+pragma solidity ^0.8.0;
+
+/**
+ * @dev Library for reading and writing primitive types to specific storage slots.
+ *
+ * Storage slots are often used to avoid storage conflict when dealing with upgradeable contracts.
+ * This library helps with reading and writing to such slots without the need for inline assembly.
+ *
+ * The functions in this library return Slot structs that contain a `value` member that can be used to read or write.
+ *
+ * Example usage to set ERC1967 implementation slot:
+ * ```
+ * contract ERC1967 {
+ *     bytes32 internal constant _IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;
+ *
+ *     function _getImplementation() internal view returns (address) {
+ *         return StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value;
+ *     }
+ *
+ *     function _setImplementation(address newImplementation) internal {
+ *         require(Address.isContract(newImplementation), "ERC1967: new implementation is not a contract");
+ *         StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value = newImplementation;
+ *     }
+ * }
+ * ```
+ *
+ * _Available since v4.1 for `address`, `bool`, `bytes32`, and `uint256`._
+ */
+library StorageSlot {
+    struct AddressSlot {
+        address value;
+    }
+
+    struct BooleanSlot {
+        bool value;
+    }
+
+    struct Bytes32Slot {
+        bytes32 value;
+    }
+
+    struct Uint256Slot {
+        uint256 value;
+    }
+
+    /**
+     * @dev Returns an `AddressSlot` with member `value` located at `slot`.
+     */
+    function getAddressSlot(bytes32 slot) internal pure returns (AddressSlot storage r) {
+        /// @solidity memory-safe-assembly
+        assembly {
+            r.slot := slot
+        }
+    }
+
+    /**
+     * @dev Returns an `BooleanSlot` with member `value` located at `slot`.
+     */
+    function getBooleanSlot(bytes32 slot) internal pure returns (BooleanSlot storage r) {
+        /// @solidity memory-safe-assembly
+        assembly {
+            r.slot := slot
+        }
+    }
+
+    /**
+     * @dev Returns an `Bytes32Slot` with member `value` located at `slot`.
+     */
+    function getBytes32Slot(bytes32 slot) internal pure returns (Bytes32Slot storage r) {
+        /// @solidity memory-safe-assembly
+        assembly {
+            r.slot := slot
+        }
+    }
+
+    /**
+     * @dev Returns an `Uint256Slot` with member `value` located at `slot`.
+     */
+    function getUint256Slot(bytes32 slot) internal pure returns (Uint256Slot storage r) {
+        /// @solidity memory-safe-assembly
+        assembly {
+            r.slot := slot
+        }
+    }
+}
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/SynthProxy.sol b/tests/unit/utils/test_data/upgradeability_util/src/SynthProxy.sol
new file mode 100644
index 000000000..9b3a6bdef
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/SynthProxy.sol
@@ -0,0 +1,58 @@
+pragma solidity ^0.5.0;
+
+contract Owned {
+    address public owner;
+
+    constructor(address _owner) public {
+        require(_owner != address(0), "Owner address cannot be 0");
+        owner = _owner;
+    }
+
+    modifier onlyOwner {
+        require(msg.sender == owner, "Only the contract owner may perform this action");
+        _;
+    }
+}
+
+contract Proxyable is Owned {
+    /* The proxy this contract exists behind. */
+    SynthProxy public proxy;
+
+    constructor(address payable _proxy) internal {
+        // This contract is abstract, and thus cannot be instantiated directly
+        require(owner != address(0), "Owner must be set");
+
+        proxy = SynthProxy(_proxy);
+    }
+
+    function setProxy(address payable _proxy) external onlyOwner {
+        proxy = SynthProxy(_proxy);
+    }
+}
+
+
+contract SynthProxy is Owned {
+    Proxyable public target;
+
+    constructor(address _owner) public Owned(_owner) {}
+
+    function setTarget(Proxyable _target) external onlyOwner {
+        target = _target;
+    }
+
+    // solhint-disable no-complex-fallback
+    function() external payable {
+        assembly {
+            calldatacopy(0, 0, calldatasize)
+
+            /* We must explicitly forward ether to the underlying contract as well. */
+            let result := delegatecall(gas, sload(target_slot), 0, calldatasize, 0, 0)
+            returndatacopy(0, 0, returndatasize)
+
+            if iszero(result) {
+                revert(0, returndatasize)
+            }
+            return(0, returndatasize)
+        }
+    }
+}
diff --git a/tests/unit/utils/test_data/upgradeability_util/src/ZosProxy.sol b/tests/unit/utils/test_data/upgradeability_util/src/ZosProxy.sol
new file mode 100644
index 000000000..db44f4c98
--- /dev/null
+++ b/tests/unit/utils/test_data/upgradeability_util/src/ZosProxy.sol
@@ -0,0 +1,67 @@
+pragma solidity ^0.5.0;
+
+contract ZosProxy {
+  function () payable external {
+    _fallback();
+  }
+
+  function _implementation() internal view returns (address);
+
+  function _delegate(address implementation) internal {
+    assembly {
+      calldatacopy(0, 0, calldatasize)
+      let result := delegatecall(gas, implementation, 0, calldatasize, 0, 0)
+      returndatacopy(0, 0, returndatasize)
+      switch result
+      case 0 { revert(0, returndatasize) }
+      default { return(0, returndatasize) }
+    }
+  }
+
+  function _willFallback() internal {
+  }
+
+  function _fallback() internal {
+    _willFallback();
+    _delegate(_implementation());
+  }
+}
+
+library AddressUtils {
+  function isContract(address addr) internal view returns (bool) {
+    uint256 size;
+    assembly { size := extcodesize(addr) }
+    return size > 0;
+  }
+}
+
+contract UpgradeabilityProxy is ZosProxy {
+  event Upgraded(address indexed implementation);
+
+  bytes32 private constant IMPLEMENTATION_SLOT = 0x7050c9e0f4ca769c69bd3a8ef740bc37934f8e2c036e5a723fd8ee048ed3f8c3;
+
+  constructor(address _implementation) public payable {
+    assert(IMPLEMENTATION_SLOT == keccak256("org.zeppelinos.proxy.implementation"));
+    _setImplementation(_implementation);
+  }
+
+  function _implementation() internal view returns (address impl) {
+    bytes32 slot = IMPLEMENTATION_SLOT;
+    assembly {
+      impl := sload(slot)
+    }
+  }
+
+  function _upgradeTo(address newImplementation) internal {
+    _setImplementation(newImplementation);
+    emit Upgraded(newImplementation);
+  }
+
+  function _setImplementation(address newImplementation) private {
+    require(AddressUtils.isContract(newImplementation), "Cannot set a proxy implementation to a non-contract address");
+    bytes32 slot = IMPLEMENTATION_SLOT;
+    assembly {
+      sstore(slot, newImplementation)
+    }
+  }
+}
diff --git a/tests/unit/utils/test_upgradeability_util.py b/tests/unit/utils/test_upgradeability_util.py
new file mode 100644
index 000000000..7d6fb82da
--- /dev/null
+++ b/tests/unit/utils/test_upgradeability_util.py
@@ -0,0 +1,85 @@
+import os
+from pathlib import Path
+
+from solc_select import solc_select
+
+from slither import Slither
+from slither.core.expressions import Literal
+from slither.utils.upgradeability import (
+    compare,
+    get_proxy_implementation_var,
+    get_proxy_implementation_slot,
+)
+
+SLITHER_ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+TEST_DATA_DIR = Path(__file__).resolve().parent / "test_data" / "upgradeability_util"
+
+
+# pylint: disable=too-many-locals
+def test_upgrades_compare() -> None:
+    solc_select.switch_global_version("0.8.2", always_install=True)
+
+    sl = Slither(os.path.join(TEST_DATA_DIR, "TestUpgrades-0.8.2.sol"))
+    v1 = sl.get_contract_from_name("ContractV1")[0]
+    v2 = sl.get_contract_from_name("ContractV2")[0]
+    missing_vars, new_vars, tainted_vars, new_funcs, modified_funcs, tainted_funcs = compare(v1, v2)
+    assert len(missing_vars) == 0
+    assert new_vars == [v2.get_state_variable_from_name("stateC")]
+    assert tainted_vars == [
+        v2.get_state_variable_from_name("stateB"),
+        v2.get_state_variable_from_name("bug"),
+    ]
+    assert new_funcs == [v2.get_function_from_signature("i()")]
+    assert modified_funcs == [v2.get_function_from_signature("checkB()")]
+    assert tainted_funcs == [
+        v2.get_function_from_signature("g(uint256)"),
+        v2.get_function_from_signature("h()"),
+    ]
+
+
+def test_upgrades_implementation_var() -> None:
+    solc_select.switch_global_version("0.8.2", always_install=True)
+    sl = Slither(os.path.join(TEST_DATA_DIR, "TestUpgrades-0.8.2.sol"))
+
+    erc_1967_proxy = sl.get_contract_from_name("ERC1967Proxy")[0]
+    storage_proxy = sl.get_contract_from_name("InheritedStorageProxy")[0]
+
+    target = get_proxy_implementation_var(erc_1967_proxy)
+    slot = get_proxy_implementation_slot(erc_1967_proxy)
+    assert target == erc_1967_proxy.get_state_variable_from_name("_IMPLEMENTATION_SLOT")
+    assert slot.slot == 0x360894A13BA1A3210667C828492DB98DCA3E2076CC3735A920A3CA505D382BBC
+    target = get_proxy_implementation_var(storage_proxy)
+    slot = get_proxy_implementation_slot(storage_proxy)
+    assert target == storage_proxy.get_state_variable_from_name("implementation")
+    assert slot.slot == 1
+
+    solc_select.switch_global_version("0.5.0", always_install=True)
+    sl = Slither(os.path.join(TEST_DATA_DIR, "TestUpgrades-0.5.0.sol"))
+
+    eip_1822_proxy = sl.get_contract_from_name("EIP1822Proxy")[0]
+    # zos_proxy = sl.get_contract_from_name("ZosProxy")[0]
+    master_copy_proxy = sl.get_contract_from_name("MasterCopyProxy")[0]
+    synth_proxy = sl.get_contract_from_name("SynthProxy")[0]
+
+    target = get_proxy_implementation_var(eip_1822_proxy)
+    slot = get_proxy_implementation_slot(eip_1822_proxy)
+    assert target not in eip_1822_proxy.state_variables_ordered
+    assert target.name == "contractLogic" and isinstance(target.expression, Literal)
+    assert (
+        target.expression.value
+        == "0xc5f16f0fcc639fa48a6947836d9850f504798523bf8c9a3a87d5876cf622bcf7"
+    )
+    assert slot.slot == 0xC5F16F0FCC639FA48A6947836D9850F504798523BF8C9A3A87D5876CF622BCF7
+    # # The util fails with this proxy due to how Slither parses assembly w/ Solidity versions < 0.6.0 (see issue #1775)
+    # target = get_proxy_implementation_var(zos_proxy)
+    # slot = get_proxy_implementation_slot(zos_proxy)
+    # assert target == zos_proxy.get_state_variable_from_name("IMPLEMENTATION_SLOT")
+    # assert slot.slot == 0x7050C9E0F4CA769C69BD3A8EF740BC37934F8E2C036E5A723FD8EE048ED3F8C3
+    target = get_proxy_implementation_var(master_copy_proxy)
+    slot = get_proxy_implementation_slot(master_copy_proxy)
+    assert target == master_copy_proxy.get_state_variable_from_name("masterCopy")
+    assert slot.slot == 0
+    target = get_proxy_implementation_var(synth_proxy)
+    slot = get_proxy_implementation_slot(synth_proxy)
+    assert target == synth_proxy.get_state_variable_from_name("target")
+    assert slot.slot == 1