diff --git a/cpp/ql/lib/ext/CAtlFileMappingBase.model.yml b/cpp/ql/lib/ext/CAtlFileMappingBase.model.yml
index dcf9fd6ca70d..e8ccc9b2fd3b 100644
--- a/cpp/ql/lib/ext/CAtlFileMappingBase.model.yml
+++ b/cpp/ql/lib/ext/CAtlFileMappingBase.model.yml
@@ -11,3 +11,4 @@ extensions:
       - ["", "CAtlFileMappingBase", True, "MapSharedMem", "", "", "Argument[*1]", "Argument[-1]", "taint", "manual"]
       - ["", "CAtlFileMappingBase", True, "OpenMapping", "", "", "Argument[*0]", "Argument[-1]", "taint", "manual"]
       - ["", "CAtlFileMappingBase", True, "operator=", "", "", "Argument[*0]", "Argument[-1]", "value", "manual"]
+      - ["", "CAtlFileMappingBase", True, "operator=", "", "", "Argument[*0]", "ReturnValue[*]", "value", "manual"]
diff --git a/cpp/ql/lib/ext/CSimpleMap.model.yml b/cpp/ql/lib/ext/CSimpleMap.model.yml
index 814e814228ed..1d9422a05611 100644
--- a/cpp/ql/lib/ext/CSimpleMap.model.yml
+++ b/cpp/ql/lib/ext/CSimpleMap.model.yml
@@ -9,4 +9,5 @@ extensions:
       - ["", "CSimpleMap", True, "SetAt", "", "", "Argument[*@1]", "Argument[-1].Element[@]", "value", "manual"]
       - ["", "CSimpleMap", True, "SetAtIndex", "", "", "Argument[*@2]", "Argument[-1].Element[@]", "value", "manual"]
       - ["", "CSimpleMap", True, "operator[]", "", "", "Argument[-1].Element[@]", "ReturnValue[*@]", "value", "manual"]
-      - ["", "CSimpleMap", True, "operator=", "", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
\ No newline at end of file
+      - ["", "CSimpleMap", True, "operator=", "", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["", "CSimpleMap", True, "operator=", "", "", "Argument[*0].Element[@]", "ReturnValue[*].Element[@]", "value", "manual"]
\ No newline at end of file
diff --git a/cpp/ql/lib/ext/CSimpleStringT.model.yml b/cpp/ql/lib/ext/CSimpleStringT.model.yml
index 820f375e791a..c5425cdc328f 100644
--- a/cpp/ql/lib/ext/CSimpleStringT.model.yml
+++ b/cpp/ql/lib/ext/CSimpleStringT.model.yml
@@ -36,6 +36,7 @@ extensions:
       - ["", "CSimpleStringT", True, "operator+=", "(wchar_t)", "", "Argument[0]", "ReturnValue[*]", "taint", "manual"]
       - ["", "CSimpleStringT", True, "operator+=", "(wchar_t)", "", "Argument[0]", "Argument[-1]", "taint", "manual"]
       - ["", "CSimpleStringT", True, "operator=", "", "", "Argument[*0]", "Argument[-1]", "value", "manual"]
+      - ["", "CSimpleStringT", True, "operator=", "", "", "Argument[*0]", "ReturnValue[*]", "value", "manual"]
       - ["", "CSimpleStringT", True, "GetAt", "", "", "Argument[-1]", "ReturnValue", "taint", "manual"]
       - ["", "CSimpleStringT", True, "GetBuffer", "", "", "Argument[-1]", "ReturnValue[*]", "value", "manual"]
       - ["", "CSimpleStringT", True, "GetBufferSetLength", "", "", "Argument[-1]", "ReturnValue[*]", "value", "manual"]
\ No newline at end of file
diff --git a/cpp/ql/lib/ext/CUrl.model.yml b/cpp/ql/lib/ext/CUrl.model.yml
index 3a4f8fe2ff5a..db51b205d4b5 100644
--- a/cpp/ql/lib/ext/CUrl.model.yml
+++ b/cpp/ql/lib/ext/CUrl.model.yml
@@ -18,4 +18,5 @@ extensions:
       - ["", "CUrl", True, "SetSchemeName", "", "", "Argument[*0]", "Argument[-1]", "taint", "manual"]
       - ["", "CUrl", True, "SetUrlPath", "", "", "Argument[*0]", "Argument[-1]", "taint", "manual"]
       - ["", "CUrl", True, "SetUserName", "", "", "Argument[*0]", "Argument[-1]", "taint", "manual"]
-      - ["", "CUrl", True, "operator=", "", "", "Argument[*0]", "Argument[-1]", "value", "manual"]
\ No newline at end of file
+      - ["", "CUrl", True, "operator=", "", "", "Argument[*0]", "Argument[-1]", "value", "manual"]
+      - ["", "CUrl", True, "operator=", "", "", "Argument[*0]", "ReturnValue[*]", "value", "manual"]
\ No newline at end of file
diff --git a/cpp/ql/lib/ext/bsl.deque.model.yml b/cpp/ql/lib/ext/bsl.deque.model.yml
index 54ac89da5111..cbdd57c97782 100644
--- a/cpp/ql/lib/ext/bsl.deque.model.yml
+++ b/cpp/ql/lib/ext/bsl.deque.model.yml
@@ -53,6 +53,7 @@ extensions:
       - ["bsl", "deque", True, "insert<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
       - ["bsl", "deque", True, "insert<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
       - ["bsl", "deque", True, "operator=", "", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["bsl", "deque", True, "operator=", "", "", "Argument[*0].Element[@]", "ReturnValue[*].Element[@]", "value", "manual"]
       - ["bsl", "deque", True, "operator[]", "", "", "Argument[-1].Element[@]", "ReturnValue[*@]", "value", "manual"]
       - ["bsl", "deque", True, "push_back", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
       - ["bsl", "deque", True, "push_front", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
diff --git a/cpp/ql/lib/ext/bsl.forward_list.model.yml b/cpp/ql/lib/ext/bsl.forward_list.model.yml
index 0f34f944626f..51ac4a157ad6 100644
--- a/cpp/ql/lib/ext/bsl.forward_list.model.yml
+++ b/cpp/ql/lib/ext/bsl.forward_list.model.yml
@@ -40,6 +40,7 @@ extensions:
       - ["bsl", "forward_list", True, "insert_after<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
       - ["bsl", "forward_list", True, "insert_after<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
       - ["bsl", "forward_list", True, "operator=", "", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["bsl", "forward_list", True, "operator=", "", "", "Argument[*0].Element[@]", "ReturnValue[*].Element[@]", "value", "manual"]
       - ["bsl", "forward_list", True, "push_front", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
       - ["bsl", "forward_list", True, "rbegin", "", "", "Argument[-1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
       - ["bsl", "forward_list", True, "rcbegin", "", "", "Argument[-1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
diff --git a/cpp/ql/lib/ext/bsl.list.model.yml b/cpp/ql/lib/ext/bsl.list.model.yml
index f4bc683db9f9..fcc1929ccac5 100644
--- a/cpp/ql/lib/ext/bsl.list.model.yml
+++ b/cpp/ql/lib/ext/bsl.list.model.yml
@@ -52,6 +52,7 @@ extensions:
       - ["bsl", "list", True, "list", "(const list &)", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
       - ["bsl", "list", True, "list", "(list &&)", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
       - ["bsl", "list", True, "operator=", "", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["bsl", "list", True, "operator=", "", "", "Argument[*0].Element[@]", "ReturnValue[*].Element[@]", "value", "manual"]
       - ["bsl", "list", True, "push_back", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
       - ["bsl", "list", True, "push_front", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
       - ["bsl", "list", True, "rbegin", "", "", "Argument[-1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
diff --git a/cpp/ql/lib/ext/bsl.vector.model.yml b/cpp/ql/lib/ext/bsl.vector.model.yml
index dc1c44ab0bea..88351b2950f9 100644
--- a/cpp/ql/lib/ext/bsl.vector.model.yml
+++ b/cpp/ql/lib/ext/bsl.vector.model.yml
@@ -39,6 +39,7 @@ extensions:
       - ["bsl", "vector", True, "insert<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
       - ["bsl", "vector", True, "insert<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
       - ["bsl", "vector", True, "operator=", "", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["bsl", "vector", True, "operator=", "", "", "Argument[*0].Element[@]", "ReturnValue[*].Element[@]", "value", "manual"]
       - ["bsl", "vector", True, "operator[]", "", "", "Argument[-1].Element[@]", "ReturnValue[*@]", "value", "manual"]
       - ["bsl", "vector", True, "push_back", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
       - ["bsl", "vector", True, "rbegin", "", "", "Argument[-1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
diff --git a/cpp/ql/lib/ext/std.deque.model.yml b/cpp/ql/lib/ext/std.deque.model.yml
index e630f224192d..f1701311e75c 100644
--- a/cpp/ql/lib/ext/std.deque.model.yml
+++ b/cpp/ql/lib/ext/std.deque.model.yml
@@ -53,6 +53,7 @@ extensions:
       - ["std", "deque", True, "insert<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
       - ["std", "deque", True, "insert<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
       - ["std", "deque", True, "operator=", "", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["std", "deque", True, "operator=", "", "", "Argument[*0].Element[@]", "ReturnValue[*].Element[@]", "value", "manual"]
       - ["std", "deque", True, "operator[]", "", "", "Argument[-1].Element[@]", "ReturnValue[*@]", "value", "manual"]
       - ["std", "deque", True, "push_back", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
       - ["std", "deque", True, "push_front", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
diff --git a/cpp/ql/lib/ext/std.forward_list.model.yml b/cpp/ql/lib/ext/std.forward_list.model.yml
index 7d0e560a6d7e..80c0d402f23e 100644
--- a/cpp/ql/lib/ext/std.forward_list.model.yml
+++ b/cpp/ql/lib/ext/std.forward_list.model.yml
@@ -40,6 +40,7 @@ extensions:
       - ["std", "forward_list", True, "insert_after<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
       - ["std", "forward_list", True, "insert_after<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
       - ["std", "forward_list", True, "operator=", "", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["std", "forward_list", True, "operator=", "", "", "Argument[*0].Element[@]", "ReturnValue[*].Element[@]", "value", "manual"]
       - ["std", "forward_list", True, "push_front", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
       - ["std", "forward_list", True, "rbegin", "", "", "Argument[-1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
       - ["std", "forward_list", True, "rcbegin", "", "", "Argument[-1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
diff --git a/cpp/ql/lib/ext/std.list.model.yml b/cpp/ql/lib/ext/std.list.model.yml
index d9ed194fe1e9..c25ac778ce0b 100644
--- a/cpp/ql/lib/ext/std.list.model.yml
+++ b/cpp/ql/lib/ext/std.list.model.yml
@@ -52,6 +52,7 @@ extensions:
       - ["std", "list", True, "list", "(const list &)", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
       - ["std", "list", True, "list", "(list &&)", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
       - ["std", "list", True, "operator=", "", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["std", "list", True, "operator=", "", "", "Argument[*0].Element[@]", "ReturnValue[*].Element[@]", "value", "manual"]
       - ["std", "list", True, "push_back", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
       - ["std", "list", True, "push_front", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
       - ["std", "list", True, "rbegin", "", "", "Argument[-1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
diff --git a/cpp/ql/lib/ext/std.vector.model.yml b/cpp/ql/lib/ext/std.vector.model.yml
index 0c8a82eca415..71d5aafb5f66 100644
--- a/cpp/ql/lib/ext/std.vector.model.yml
+++ b/cpp/ql/lib/ext/std.vector.model.yml
@@ -39,6 +39,7 @@ extensions:
       - ["std", "vector", True, "insert<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
       - ["std", "vector", True, "insert<InputIt>", "(const_iterator,InputIt,InputIt)", "", "Argument[1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
       - ["std", "vector", True, "operator=", "", "", "Argument[*0].Element[@]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["std", "vector", True, "operator=", "", "", "Argument[*0].Element[@]", "ReturnValue[*].Element[@]", "value", "manual"]
       - ["std", "vector", True, "operator[]", "", "", "Argument[-1].Element[@]", "ReturnValue[*@]", "value", "manual"]
       - ["std", "vector", True, "push_back", "", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
       - ["std", "vector", True, "rbegin", "", "", "Argument[-1].Element[@]", "ReturnValue.Element[@]", "value", "manual"]
diff --git a/cpp/ql/test/library-tests/dataflow/external-models/flow.expected b/cpp/ql/test/library-tests/dataflow/external-models/flow.expected
index c370e57bc13b..eb58dc0a9c77 100644
--- a/cpp/ql/test/library-tests/dataflow/external-models/flow.expected
+++ b/cpp/ql/test/library-tests/dataflow/external-models/flow.expected
@@ -10,14 +10,14 @@ edges
 | asio_streams.cpp:100:44:100:62 | call to buffer | asio_streams.cpp:103:29:103:39 | *send_buffer | provenance | Sink:MaD:6 |
 | asio_streams.cpp:100:64:100:71 | *send_str | asio_streams.cpp:56:18:56:23 | [summary param] *0 in buffer | provenance |  |
 | asio_streams.cpp:100:64:100:71 | *send_str | asio_streams.cpp:100:44:100:62 | call to buffer | provenance | MaD:10 |
-| test.cpp:4:5:4:11 | [summary param] 0 in ymlStep | test.cpp:4:5:4:11 | [summary] to write: ReturnValue in ymlStep | provenance | MaD:954 |
-| test.cpp:7:10:7:18 | call to ymlSource | test.cpp:7:10:7:18 | call to ymlSource | provenance | Src:MaD:952  |
-| test.cpp:7:10:7:18 | call to ymlSource | test.cpp:11:10:11:10 | x | provenance | Sink:MaD:953 |
+| test.cpp:4:5:4:11 | [summary param] 0 in ymlStep | test.cpp:4:5:4:11 | [summary] to write: ReturnValue in ymlStep | provenance | MaD:966 |
+| test.cpp:7:10:7:18 | call to ymlSource | test.cpp:7:10:7:18 | call to ymlSource | provenance | Src:MaD:964  |
+| test.cpp:7:10:7:18 | call to ymlSource | test.cpp:11:10:11:10 | x | provenance | Sink:MaD:965 |
 | test.cpp:7:10:7:18 | call to ymlSource | test.cpp:13:18:13:18 | x | provenance |  |
 | test.cpp:13:10:13:16 | call to ymlStep | test.cpp:13:10:13:16 | call to ymlStep | provenance |  |
-| test.cpp:13:10:13:16 | call to ymlStep | test.cpp:15:10:15:10 | y | provenance | Sink:MaD:953 |
+| test.cpp:13:10:13:16 | call to ymlStep | test.cpp:15:10:15:10 | y | provenance | Sink:MaD:965 |
 | test.cpp:13:18:13:18 | x | test.cpp:4:5:4:11 | [summary param] 0 in ymlStep | provenance |  |
-| test.cpp:13:18:13:18 | x | test.cpp:13:10:13:16 | call to ymlStep | provenance | MaD:954 |
+| test.cpp:13:18:13:18 | x | test.cpp:13:10:13:16 | call to ymlStep | provenance | MaD:966 |
 nodes
 | asio_streams.cpp:56:18:56:23 | [summary param] *0 in buffer | semmle.label | [summary param] *0 in buffer |
 | asio_streams.cpp:56:18:56:23 | [summary] to write: ReturnValue in buffer | semmle.label | [summary] to write: ReturnValue in buffer |