diff --git a/change-notes/1.26/analysis-javascript.md b/change-notes/1.26/analysis-javascript.md
index 61036ad102d..392e4bebeb7 100644
--- a/change-notes/1.26/analysis-javascript.md
+++ b/change-notes/1.26/analysis-javascript.md
@@ -35,6 +35,7 @@
 | Unused loop iteration variable (`js/unused-loop-variable`) | Fewer results | This query no longer flags variables in a destructuring array assignment that are not the last variable in the destructed array. |
 | Unsafe shell command constructed from library input (`js/shell-command-constructed-from-input`) | More results | This query now recognizes more commands where colon, dash, and underscore are used. |
 | Unsafe jQuery plugin (`js/unsafe-jquery-plugin`) | More results | This query now detects more unsafe uses of nested option properties. |
+| Client-side URL redirect (`js/client-side-unvalidated-url-redirection`) | More results | This query now recognizes some unsafe uses of `importScripts()` inside WebWorkers. |
 
 
 ## Changes to libraries
diff --git a/javascript/ql/src/semmle/javascript/security/dataflow/ClientSideUrlRedirectCustomizations.qll b/javascript/ql/src/semmle/javascript/security/dataflow/ClientSideUrlRedirectCustomizations.qll
index 358de5e8900..64c76a84b82 100644
--- a/javascript/ql/src/semmle/javascript/security/dataflow/ClientSideUrlRedirectCustomizations.qll
+++ b/javascript/ql/src/semmle/javascript/security/dataflow/ClientSideUrlRedirectCustomizations.qll
@@ -132,6 +132,15 @@ module ClientSideUrlRedirect {
     }
   }
 
+  /**
+   * An argument to `importScripts(..)` - which is used inside `WebWorker`s to import new scripts - viewed as a `ScriptUrlSink`.
+   */
+  class ImportScriptsSink extends ScriptUrlSink {
+    ImportScriptsSink() {
+      this = DataFlow::globalVarRef("importScripts").getACall().getAnArgument()
+    }
+  }
+
   /**
    * A script or iframe `src` attribute, viewed as a `ScriptUrlSink`.
    */
diff --git a/javascript/ql/src/semmle/javascript/security/dataflow/DOM.qll b/javascript/ql/src/semmle/javascript/security/dataflow/DOM.qll
index f9882537b4e..57d5612f35e 100644
--- a/javascript/ql/src/semmle/javascript/security/dataflow/DOM.qll
+++ b/javascript/ql/src/semmle/javascript/security/dataflow/DOM.qll
@@ -199,6 +199,11 @@ class PostMessageEventHandler extends Function {
       addEventListener.getArgument(0).mayHaveStringValue("message") and
       addEventListener.getArgument(1).getABoundFunctionValue(paramIndex).getFunction() = this
     )
+    or
+    exists(DataFlow::Node rhs |
+      rhs = DataFlow::globalObjectRef().getAPropertyWrite("onmessage").getRhs() and
+      rhs.getABoundFunctionValue(paramIndex).getFunction() = this
+    )
   }
 
   /**
diff --git a/javascript/ql/test/query-tests/Security/CWE-601/ClientSideUrlRedirect/ClientSideUrlRedirect.expected b/javascript/ql/test/query-tests/Security/CWE-601/ClientSideUrlRedirect/ClientSideUrlRedirect.expected
index 506dcf1ee0a..b7dca317a88 100644
--- a/javascript/ql/test/query-tests/Security/CWE-601/ClientSideUrlRedirect/ClientSideUrlRedirect.expected
+++ b/javascript/ql/test/query-tests/Security/CWE-601/ClientSideUrlRedirect/ClientSideUrlRedirect.expected
@@ -113,6 +113,14 @@ nodes
 | tst13.js:40:15:40:21 | payload |
 | tst13.js:44:14:44:20 | payload |
 | tst13.js:44:14:44:20 | payload |
+| tst13.js:49:32:49:32 | e |
+| tst13.js:49:32:49:32 | e |
+| tst13.js:50:23:50:23 | e |
+| tst13.js:50:23:50:23 | e |
+| tst13.js:52:34:52:34 | e |
+| tst13.js:52:34:52:34 | e |
+| tst13.js:53:28:53:28 | e |
+| tst13.js:53:28:53:28 | e |
 | tst.js:2:19:2:69 | /.*redi ... n.href) |
 | tst.js:2:19:2:72 | /.*redi ... ref)[1] |
 | tst.js:2:19:2:72 | /.*redi ... ref)[1] |
@@ -234,6 +242,14 @@ edges
 | tst13.js:2:19:2:35 | document.location | tst13.js:2:19:2:42 | documen ... .search |
 | tst13.js:2:19:2:42 | documen ... .search | tst13.js:2:19:2:52 | documen ... bstr(1) |
 | tst13.js:2:19:2:52 | documen ... bstr(1) | tst13.js:2:9:2:52 | payload |
+| tst13.js:49:32:49:32 | e | tst13.js:50:23:50:23 | e |
+| tst13.js:49:32:49:32 | e | tst13.js:50:23:50:23 | e |
+| tst13.js:49:32:49:32 | e | tst13.js:50:23:50:23 | e |
+| tst13.js:49:32:49:32 | e | tst13.js:50:23:50:23 | e |
+| tst13.js:52:34:52:34 | e | tst13.js:53:28:53:28 | e |
+| tst13.js:52:34:52:34 | e | tst13.js:53:28:53:28 | e |
+| tst13.js:52:34:52:34 | e | tst13.js:53:28:53:28 | e |
+| tst13.js:52:34:52:34 | e | tst13.js:53:28:53:28 | e |
 | tst.js:2:19:2:69 | /.*redi ... n.href) | tst.js:2:19:2:72 | /.*redi ... ref)[1] |
 | tst.js:2:19:2:69 | /.*redi ... n.href) | tst.js:2:19:2:72 | /.*redi ... ref)[1] |
 | tst.js:2:47:2:63 | document.location | tst.js:2:47:2:68 | documen ... on.href |
@@ -276,5 +292,7 @@ edges
 | tst13.js:36:21:36:27 | payload | tst13.js:2:19:2:35 | document.location | tst13.js:36:21:36:27 | payload | Untrusted URL redirection due to $@. | tst13.js:2:19:2:35 | document.location | user-provided value |
 | tst13.js:40:15:40:21 | payload | tst13.js:2:19:2:35 | document.location | tst13.js:40:15:40:21 | payload | Untrusted URL redirection due to $@. | tst13.js:2:19:2:35 | document.location | user-provided value |
 | tst13.js:44:14:44:20 | payload | tst13.js:2:19:2:35 | document.location | tst13.js:44:14:44:20 | payload | Untrusted URL redirection due to $@. | tst13.js:2:19:2:35 | document.location | user-provided value |
+| tst13.js:50:23:50:23 | e | tst13.js:49:32:49:32 | e | tst13.js:50:23:50:23 | e | Untrusted URL redirection due to $@. | tst13.js:49:32:49:32 | e | user-provided value |
+| tst13.js:53:28:53:28 | e | tst13.js:52:34:52:34 | e | tst13.js:53:28:53:28 | e | Untrusted URL redirection due to $@. | tst13.js:52:34:52:34 | e | user-provided value |
 | tst.js:2:19:2:72 | /.*redi ... ref)[1] | tst.js:2:47:2:63 | document.location | tst.js:2:19:2:72 | /.*redi ... ref)[1] | Untrusted URL redirection due to $@. | tst.js:2:47:2:63 | document.location | user-provided value |
 | tst.js:6:20:6:59 | indirec ... ref)[1] | tst.js:6:34:6:50 | document.location | tst.js:6:20:6:59 | indirec ... ref)[1] | Untrusted URL redirection due to $@. | tst.js:6:34:6:50 | document.location | user-provided value |
diff --git a/javascript/ql/test/query-tests/Security/CWE-601/ClientSideUrlRedirect/tst13.js b/javascript/ql/test/query-tests/Security/CWE-601/ClientSideUrlRedirect/tst13.js
index 72c9c0b6e72..7a71cf06c08 100644
--- a/javascript/ql/test/query-tests/Security/CWE-601/ClientSideUrlRedirect/tst13.js
+++ b/javascript/ql/test/query-tests/Security/CWE-601/ClientSideUrlRedirect/tst13.js
@@ -44,3 +44,12 @@ function foo() {
     el.src = payload;
     document.body.appendChild(el); // NOT OK
 }
+
+(function () {
+    self.onmessage = function (e) {
+        importScripts(e); // NOT OK
+    }
+    window.onmessage = function (e) {
+        self.importScripts(e); // NOT OK
+    }
+})();