diff --git a/components/password_manager/content/browser/content_password_manager_driver.cc b/components/password_manager/content/browser/content_password_manager_driver.cc
index 28f7beb14e7af..3cf254f02c52a 100644
--- a/components/password_manager/content/browser/content_password_manager_driver.cc
+++ b/components/password_manager/content/browser/content_password_manager_driver.cc
@@ -208,8 +208,27 @@ void ContentPasswordManagerDriver::PropagateFillDataOnParsingCompletion(
     password_autofill_manager_.OnAddPasswordFillData(form_data);
   }
   if (const auto& agent = GetPasswordAutofillAgent()) {
+    // Defense in depth: the kCrossOriginIframe gate in
+    // SendFillInformationToRenderer() compares only the primary main frame
+    // against this frame. Walk the full ancestor chain here so a same-origin
+    // subframe sandwiched under a cross-origin intermediate ancestor never
+    // receives cleartext password values over IPC. This brings the
+    // browser-side gate to parity with the renderer-side
+    // IsInCrossOriginIframeOrEmbeddedFrame() check.
+    autofill::PasswordFormFillData to_send = form_data;
+    if (!to_send.wait_for_username) {
+      const url::Origin& target = render_frame_host_->GetLastCommittedOrigin();
+      for (content::RenderFrameHost* ancestor =
+               render_frame_host_->GetParentOrOuterDocument();
+           ancestor; ancestor = ancestor->GetParentOrOuterDocument()) {
+        if (!target.IsSameOriginWith(ancestor->GetLastCommittedOrigin())) {
+          to_send.wait_for_username = true;
+          break;
+        }
+      }
+    }
     agent->ApplyFillDataOnParsingCompletion(
-        autofill::MaybeClearPasswordValues(form_data));
+        autofill::MaybeClearPasswordValues(to_send));
   }
 }