diff --git a/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPublic.qll b/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPublic.qll
index aa86d0aecc9..3a33a71710e 100644
--- a/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPublic.qll
+++ b/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPublic.qll
@@ -643,3 +643,20 @@ class AttributeContent extends TAttributeContent, Content {
 
   override string toString() { result = "Attribute " + attr }
 }
+
+/**
+ * An entity that represents a set of `Content`s.
+ *
+ * The set may be interpreted differently depending on whether it is
+ * stored into (`getAStoreContent`) or read from (`getAReadContent`).
+ */
+class ContentSet instanceof Content {
+  /** Gets a content that may be stored into when storing into this set. */
+  Content getAStoreContent() { result = this }
+
+  /** Gets a content that may be read from when reading from this set. */
+  Content getAReadContent() { result = this }
+
+  /** Gets a textual representation of this content set. */
+  string toString() { result = super.toString() }
+}
diff --git a/python/ql/test/query-tests/Security/CWE-090-LdapInjection/LdapInjection.expected b/python/ql/test/query-tests/Security/CWE-090-LdapInjection/LdapInjection.expected
index add8d88cafa..a003f56b09f 100644
--- a/python/ql/test/query-tests/Security/CWE-090-LdapInjection/LdapInjection.expected
+++ b/python/ql/test/query-tests/Security/CWE-090-LdapInjection/LdapInjection.expected
@@ -1,6 +1,5 @@
 edges
 | ldap3_bad.py:13:17:13:23 | ControlFlowNode for request | ldap3_bad.py:13:17:13:28 | ControlFlowNode for Attribute |
-| ldap3_bad.py:13:17:13:23 | ControlFlowNode for request | ldap3_bad.py:14:21:14:27 | ControlFlowNode for request |
 | ldap3_bad.py:13:17:13:23 | ControlFlowNode for request | ldap3_bad.py:14:21:14:32 | ControlFlowNode for Attribute |
 | ldap3_bad.py:13:17:13:28 | ControlFlowNode for Attribute | ldap3_bad.py:13:17:13:34 | ControlFlowNode for Subscript |
 | ldap3_bad.py:13:17:13:34 | ControlFlowNode for Subscript | ldap3_bad.py:21:17:21:18 | ControlFlowNode for dn |
@@ -8,7 +7,6 @@ edges
 | ldap3_bad.py:14:21:14:32 | ControlFlowNode for Attribute | ldap3_bad.py:14:21:14:44 | ControlFlowNode for Subscript |
 | ldap3_bad.py:14:21:14:44 | ControlFlowNode for Subscript | ldap3_bad.py:21:21:21:33 | ControlFlowNode for search_filter |
 | ldap3_bad.py:30:17:30:23 | ControlFlowNode for request | ldap3_bad.py:30:17:30:28 | ControlFlowNode for Attribute |
-| ldap3_bad.py:30:17:30:23 | ControlFlowNode for request | ldap3_bad.py:31:21:31:27 | ControlFlowNode for request |
 | ldap3_bad.py:30:17:30:23 | ControlFlowNode for request | ldap3_bad.py:31:21:31:32 | ControlFlowNode for Attribute |
 | ldap3_bad.py:30:17:30:28 | ControlFlowNode for Attribute | ldap3_bad.py:30:17:30:34 | ControlFlowNode for Subscript |
 | ldap3_bad.py:30:17:30:34 | ControlFlowNode for Subscript | ldap3_bad.py:38:9:38:10 | ControlFlowNode for dn |
@@ -16,7 +14,6 @@ edges
 | ldap3_bad.py:31:21:31:32 | ControlFlowNode for Attribute | ldap3_bad.py:31:21:31:44 | ControlFlowNode for Subscript |
 | ldap3_bad.py:31:21:31:44 | ControlFlowNode for Subscript | ldap3_bad.py:38:13:38:25 | ControlFlowNode for search_filter |
 | ldap_bad.py:13:17:13:23 | ControlFlowNode for request | ldap_bad.py:13:17:13:28 | ControlFlowNode for Attribute |
-| ldap_bad.py:13:17:13:23 | ControlFlowNode for request | ldap_bad.py:14:21:14:27 | ControlFlowNode for request |
 | ldap_bad.py:13:17:13:23 | ControlFlowNode for request | ldap_bad.py:14:21:14:32 | ControlFlowNode for Attribute |
 | ldap_bad.py:13:17:13:28 | ControlFlowNode for Attribute | ldap_bad.py:13:17:13:34 | ControlFlowNode for Subscript |
 | ldap_bad.py:13:17:13:34 | ControlFlowNode for Subscript | ldap_bad.py:21:9:21:10 | ControlFlowNode for dn |
@@ -24,7 +21,6 @@ edges
 | ldap_bad.py:14:21:14:32 | ControlFlowNode for Attribute | ldap_bad.py:14:21:14:44 | ControlFlowNode for Subscript |
 | ldap_bad.py:14:21:14:44 | ControlFlowNode for Subscript | ldap_bad.py:21:33:21:45 | ControlFlowNode for search_filter |
 | ldap_bad.py:30:17:30:23 | ControlFlowNode for request | ldap_bad.py:30:17:30:28 | ControlFlowNode for Attribute |
-| ldap_bad.py:30:17:30:23 | ControlFlowNode for request | ldap_bad.py:31:21:31:27 | ControlFlowNode for request |
 | ldap_bad.py:30:17:30:23 | ControlFlowNode for request | ldap_bad.py:31:21:31:32 | ControlFlowNode for Attribute |
 | ldap_bad.py:30:17:30:28 | ControlFlowNode for Attribute | ldap_bad.py:30:17:30:34 | ControlFlowNode for Subscript |
 | ldap_bad.py:30:17:30:34 | ControlFlowNode for Subscript | ldap_bad.py:37:9:37:10 | ControlFlowNode for dn |
@@ -32,7 +28,6 @@ edges
 | ldap_bad.py:31:21:31:32 | ControlFlowNode for Attribute | ldap_bad.py:31:21:31:44 | ControlFlowNode for Subscript |
 | ldap_bad.py:31:21:31:44 | ControlFlowNode for Subscript | ldap_bad.py:37:33:37:45 | ControlFlowNode for search_filter |
 | ldap_bad.py:47:17:47:23 | ControlFlowNode for request | ldap_bad.py:47:17:47:28 | ControlFlowNode for Attribute |
-| ldap_bad.py:47:17:47:23 | ControlFlowNode for request | ldap_bad.py:48:21:48:27 | ControlFlowNode for request |
 | ldap_bad.py:47:17:47:23 | ControlFlowNode for request | ldap_bad.py:48:21:48:32 | ControlFlowNode for Attribute |
 | ldap_bad.py:47:17:47:28 | ControlFlowNode for Attribute | ldap_bad.py:47:17:47:34 | ControlFlowNode for Subscript |
 | ldap_bad.py:47:17:47:34 | ControlFlowNode for Subscript | ldap_bad.py:55:9:55:10 | ControlFlowNode for dn |
diff --git a/python/ql/test/query-tests/Security/CWE-918-ServerSideRequestForgery/FullServerSideRequestForgery.expected b/python/ql/test/query-tests/Security/CWE-918-ServerSideRequestForgery/FullServerSideRequestForgery.expected
index 24b46bcd248..cc55c8317e1 100644
--- a/python/ql/test/query-tests/Security/CWE-918-ServerSideRequestForgery/FullServerSideRequestForgery.expected
+++ b/python/ql/test/query-tests/Security/CWE-918-ServerSideRequestForgery/FullServerSideRequestForgery.expected
@@ -1,7 +1,6 @@
 edges
 | full_partial_test.py:7:18:7:24 | ControlFlowNode for request | full_partial_test.py:7:18:7:29 | ControlFlowNode for Attribute |
 | full_partial_test.py:7:18:7:24 | ControlFlowNode for request | full_partial_test.py:7:18:7:29 | ControlFlowNode for Attribute |
-| full_partial_test.py:7:18:7:24 | ControlFlowNode for request | full_partial_test.py:8:17:8:23 | ControlFlowNode for request |
 | full_partial_test.py:7:18:7:24 | ControlFlowNode for request | full_partial_test.py:8:17:8:28 | ControlFlowNode for Attribute |
 | full_partial_test.py:7:18:7:29 | ControlFlowNode for Attribute | full_partial_test.py:7:18:7:48 | ControlFlowNode for Subscript |
 | full_partial_test.py:7:18:7:29 | ControlFlowNode for Attribute | full_partial_test.py:7:18:7:48 | ControlFlowNode for Subscript |
@@ -18,7 +17,6 @@ edges
 | full_partial_test.py:8:17:8:41 | ControlFlowNode for Subscript | full_partial_test.py:23:18:23:20 | ControlFlowNode for url |
 | full_partial_test.py:37:18:37:24 | ControlFlowNode for request | full_partial_test.py:37:18:37:29 | ControlFlowNode for Attribute |
 | full_partial_test.py:37:18:37:24 | ControlFlowNode for request | full_partial_test.py:37:18:37:29 | ControlFlowNode for Attribute |
-| full_partial_test.py:37:18:37:24 | ControlFlowNode for request | full_partial_test.py:38:17:38:23 | ControlFlowNode for request |
 | full_partial_test.py:37:18:37:24 | ControlFlowNode for request | full_partial_test.py:38:17:38:28 | ControlFlowNode for Attribute |
 | full_partial_test.py:37:18:37:29 | ControlFlowNode for Attribute | full_partial_test.py:37:18:37:48 | ControlFlowNode for Subscript |
 | full_partial_test.py:37:18:37:29 | ControlFlowNode for Attribute | full_partial_test.py:37:18:37:48 | ControlFlowNode for Subscript |
@@ -37,7 +35,6 @@ edges
 | full_partial_test.py:38:17:38:41 | ControlFlowNode for Subscript | full_partial_test.py:48:18:48:20 | ControlFlowNode for url |
 | full_partial_test.py:57:18:57:24 | ControlFlowNode for request | full_partial_test.py:57:18:57:29 | ControlFlowNode for Attribute |
 | full_partial_test.py:57:18:57:24 | ControlFlowNode for request | full_partial_test.py:57:18:57:29 | ControlFlowNode for Attribute |
-| full_partial_test.py:57:18:57:24 | ControlFlowNode for request | full_partial_test.py:58:17:58:23 | ControlFlowNode for request |
 | full_partial_test.py:57:18:57:24 | ControlFlowNode for request | full_partial_test.py:58:17:58:28 | ControlFlowNode for Attribute |
 | full_partial_test.py:57:18:57:29 | ControlFlowNode for Attribute | full_partial_test.py:57:18:57:48 | ControlFlowNode for Subscript |
 | full_partial_test.py:57:18:57:29 | ControlFlowNode for Attribute | full_partial_test.py:57:18:57:48 | ControlFlowNode for Subscript |
@@ -52,7 +49,6 @@ edges
 | full_partial_test.py:67:38:67:58 | ControlFlowNode for Tuple | full_partial_test.py:68:18:68:20 | ControlFlowNode for url |
 | full_partial_test.py:71:18:71:24 | ControlFlowNode for request | full_partial_test.py:71:18:71:29 | ControlFlowNode for Attribute |
 | full_partial_test.py:71:18:71:24 | ControlFlowNode for request | full_partial_test.py:71:18:71:29 | ControlFlowNode for Attribute |
-| full_partial_test.py:71:18:71:24 | ControlFlowNode for request | full_partial_test.py:72:17:72:23 | ControlFlowNode for request |
 | full_partial_test.py:71:18:71:24 | ControlFlowNode for request | full_partial_test.py:72:17:72:28 | ControlFlowNode for Attribute |
 | full_partial_test.py:71:18:71:29 | ControlFlowNode for Attribute | full_partial_test.py:71:18:71:48 | ControlFlowNode for Subscript |
 | full_partial_test.py:71:18:71:29 | ControlFlowNode for Attribute | full_partial_test.py:71:18:71:48 | ControlFlowNode for Subscript |
@@ -85,11 +81,8 @@ edges
 | full_partial_test.py:119:18:119:48 | ControlFlowNode for Subscript | full_partial_test.py:122:18:122:20 | ControlFlowNode for url |
 | test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:9:19:9:30 | ControlFlowNode for Attribute |
 | test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:9:19:9:30 | ControlFlowNode for Attribute |
-| test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:10:19:10:25 | ControlFlowNode for request |
-| test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:10:19:10:25 | ControlFlowNode for request |
 | test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute |
 | test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute |
-| test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:11:18:11:24 | ControlFlowNode for request |
 | test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:11:18:11:29 | ControlFlowNode for Attribute |
 | test_http_client.py:9:19:9:30 | ControlFlowNode for Attribute | test_http_client.py:9:19:9:38 | ControlFlowNode for Subscript |
 | test_http_client.py:9:19:9:30 | ControlFlowNode for Attribute | test_http_client.py:9:19:9:38 | ControlFlowNode for Subscript |
@@ -101,7 +94,6 @@ edges
 | test_http_client.py:9:19:9:38 | ControlFlowNode for Subscript | test_http_client.py:25:27:25:37 | ControlFlowNode for unsafe_host |
 | test_http_client.py:10:19:10:25 | ControlFlowNode for request | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute |
 | test_http_client.py:10:19:10:25 | ControlFlowNode for request | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute |
-| test_http_client.py:10:19:10:25 | ControlFlowNode for request | test_http_client.py:11:18:11:24 | ControlFlowNode for request |
 | test_http_client.py:10:19:10:25 | ControlFlowNode for request | test_http_client.py:11:18:11:29 | ControlFlowNode for Attribute |
 | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute | test_http_client.py:10:19:10:38 | ControlFlowNode for Subscript |
 | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute | test_http_client.py:10:19:10:38 | ControlFlowNode for Subscript |
diff --git a/python/ql/test/query-tests/Security/CWE-918-ServerSideRequestForgery/PartialServerSideRequestForgery.expected b/python/ql/test/query-tests/Security/CWE-918-ServerSideRequestForgery/PartialServerSideRequestForgery.expected
index 2a5000aa742..6206a070a88 100644
--- a/python/ql/test/query-tests/Security/CWE-918-ServerSideRequestForgery/PartialServerSideRequestForgery.expected
+++ b/python/ql/test/query-tests/Security/CWE-918-ServerSideRequestForgery/PartialServerSideRequestForgery.expected
@@ -1,7 +1,6 @@
 edges
 | full_partial_test.py:7:18:7:24 | ControlFlowNode for request | full_partial_test.py:7:18:7:29 | ControlFlowNode for Attribute |
 | full_partial_test.py:7:18:7:24 | ControlFlowNode for request | full_partial_test.py:7:18:7:29 | ControlFlowNode for Attribute |
-| full_partial_test.py:7:18:7:24 | ControlFlowNode for request | full_partial_test.py:8:17:8:23 | ControlFlowNode for request |
 | full_partial_test.py:7:18:7:24 | ControlFlowNode for request | full_partial_test.py:8:17:8:28 | ControlFlowNode for Attribute |
 | full_partial_test.py:7:18:7:29 | ControlFlowNode for Attribute | full_partial_test.py:7:18:7:48 | ControlFlowNode for Subscript |
 | full_partial_test.py:7:18:7:29 | ControlFlowNode for Attribute | full_partial_test.py:7:18:7:48 | ControlFlowNode for Subscript |
@@ -18,7 +17,6 @@ edges
 | full_partial_test.py:8:17:8:41 | ControlFlowNode for Subscript | full_partial_test.py:23:18:23:20 | ControlFlowNode for url |
 | full_partial_test.py:37:18:37:24 | ControlFlowNode for request | full_partial_test.py:37:18:37:29 | ControlFlowNode for Attribute |
 | full_partial_test.py:37:18:37:24 | ControlFlowNode for request | full_partial_test.py:37:18:37:29 | ControlFlowNode for Attribute |
-| full_partial_test.py:37:18:37:24 | ControlFlowNode for request | full_partial_test.py:38:17:38:23 | ControlFlowNode for request |
 | full_partial_test.py:37:18:37:24 | ControlFlowNode for request | full_partial_test.py:38:17:38:28 | ControlFlowNode for Attribute |
 | full_partial_test.py:37:18:37:29 | ControlFlowNode for Attribute | full_partial_test.py:37:18:37:48 | ControlFlowNode for Subscript |
 | full_partial_test.py:37:18:37:29 | ControlFlowNode for Attribute | full_partial_test.py:37:18:37:48 | ControlFlowNode for Subscript |
@@ -37,7 +35,6 @@ edges
 | full_partial_test.py:38:17:38:41 | ControlFlowNode for Subscript | full_partial_test.py:48:18:48:20 | ControlFlowNode for url |
 | full_partial_test.py:57:18:57:24 | ControlFlowNode for request | full_partial_test.py:57:18:57:29 | ControlFlowNode for Attribute |
 | full_partial_test.py:57:18:57:24 | ControlFlowNode for request | full_partial_test.py:57:18:57:29 | ControlFlowNode for Attribute |
-| full_partial_test.py:57:18:57:24 | ControlFlowNode for request | full_partial_test.py:58:17:58:23 | ControlFlowNode for request |
 | full_partial_test.py:57:18:57:24 | ControlFlowNode for request | full_partial_test.py:58:17:58:28 | ControlFlowNode for Attribute |
 | full_partial_test.py:57:18:57:29 | ControlFlowNode for Attribute | full_partial_test.py:57:18:57:48 | ControlFlowNode for Subscript |
 | full_partial_test.py:57:18:57:29 | ControlFlowNode for Attribute | full_partial_test.py:57:18:57:48 | ControlFlowNode for Subscript |
@@ -52,7 +49,6 @@ edges
 | full_partial_test.py:67:38:67:58 | ControlFlowNode for Tuple | full_partial_test.py:68:18:68:20 | ControlFlowNode for url |
 | full_partial_test.py:71:18:71:24 | ControlFlowNode for request | full_partial_test.py:71:18:71:29 | ControlFlowNode for Attribute |
 | full_partial_test.py:71:18:71:24 | ControlFlowNode for request | full_partial_test.py:71:18:71:29 | ControlFlowNode for Attribute |
-| full_partial_test.py:71:18:71:24 | ControlFlowNode for request | full_partial_test.py:72:17:72:23 | ControlFlowNode for request |
 | full_partial_test.py:71:18:71:24 | ControlFlowNode for request | full_partial_test.py:72:17:72:28 | ControlFlowNode for Attribute |
 | full_partial_test.py:71:18:71:29 | ControlFlowNode for Attribute | full_partial_test.py:71:18:71:48 | ControlFlowNode for Subscript |
 | full_partial_test.py:71:18:71:29 | ControlFlowNode for Attribute | full_partial_test.py:71:18:71:48 | ControlFlowNode for Subscript |
@@ -85,11 +81,8 @@ edges
 | full_partial_test.py:119:18:119:48 | ControlFlowNode for Subscript | full_partial_test.py:122:18:122:20 | ControlFlowNode for url |
 | test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:9:19:9:30 | ControlFlowNode for Attribute |
 | test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:9:19:9:30 | ControlFlowNode for Attribute |
-| test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:10:19:10:25 | ControlFlowNode for request |
-| test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:10:19:10:25 | ControlFlowNode for request |
 | test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute |
 | test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute |
-| test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:11:18:11:24 | ControlFlowNode for request |
 | test_http_client.py:9:19:9:25 | ControlFlowNode for request | test_http_client.py:11:18:11:29 | ControlFlowNode for Attribute |
 | test_http_client.py:9:19:9:30 | ControlFlowNode for Attribute | test_http_client.py:9:19:9:38 | ControlFlowNode for Subscript |
 | test_http_client.py:9:19:9:30 | ControlFlowNode for Attribute | test_http_client.py:9:19:9:38 | ControlFlowNode for Subscript |
@@ -101,7 +94,6 @@ edges
 | test_http_client.py:9:19:9:38 | ControlFlowNode for Subscript | test_http_client.py:25:27:25:37 | ControlFlowNode for unsafe_host |
 | test_http_client.py:10:19:10:25 | ControlFlowNode for request | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute |
 | test_http_client.py:10:19:10:25 | ControlFlowNode for request | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute |
-| test_http_client.py:10:19:10:25 | ControlFlowNode for request | test_http_client.py:11:18:11:24 | ControlFlowNode for request |
 | test_http_client.py:10:19:10:25 | ControlFlowNode for request | test_http_client.py:11:18:11:29 | ControlFlowNode for Attribute |
 | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute | test_http_client.py:10:19:10:38 | ControlFlowNode for Subscript |
 | test_http_client.py:10:19:10:30 | ControlFlowNode for Attribute | test_http_client.py:10:19:10:38 | ControlFlowNode for Subscript |