From b5de58dc9173aac7795109e23a85f892dc4005df Mon Sep 17 00:00:00 2001
From: Pete Miller <miller.pete@gmail.com>
Date: Thu, 27 Nov 2025 04:09:21 -0800
Subject: [PATCH] [AI Chat] [Content Agent] Block navigation to and using tools
 on extension store pages (#32576)

---
 .../content_agent_tools_browsertest.cc        | 34 +++++++++++++++++++
 .../chrome/browser/actor/site_policy.cc       | 34 +++++++++++++++++++
 .../chrome-browser-actor-site_policy.cc.patch | 12 +++++++
 3 files changed, 80 insertions(+)
 create mode 100644 chromium_src/chrome/browser/actor/site_policy.cc
 create mode 100644 patches/chrome-browser-actor-site_policy.cc.patch

diff --git a/browser/ai_chat/content_agent_tools_browsertest.cc b/browser/ai_chat/content_agent_tools_browsertest.cc
index d93665684aa..e9d2af944d8 100644
--- a/browser/ai_chat/content_agent_tools_browsertest.cc
+++ b/browser/ai_chat/content_agent_tools_browsertest.cc
@@ -19,6 +19,7 @@
 #include "brave/components/ai_chat/core/common/features.h"
 #include "brave/components/ai_chat/core/common/test_utils.h"
 #include "chrome/browser/actor/actor_keyed_service_factory.h"
+#include "chrome/browser/actor/actor_policy_checker.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/test/base/in_process_browser_test.h"
@@ -348,6 +349,39 @@ IN_PROC_BROWSER_TEST_F(ContentAgentToolsTest, NavigationTool_BasicNavigation) {
   EXPECT_EQ(test_url.path(), final_url.path());
 }
 
+IN_PROC_BROWSER_TEST_F(ContentAgentToolsTest, BlockExtensionStore) {
+  // Verify that navigating to the extension store is blocked
+  NavigateToChromiumTestFile("/actor/page_with_clickable_element.html");
+
+  auto nav_tool = FindToolByName("web_page_navigator");
+  ASSERT_TRUE(nav_tool);
+
+  // Get initial URL
+  GURL initial_url = web_contents()->GetVisibleURL();
+
+  // Create input for navigating to a different test page
+  base::Value::Dict input;
+  input.Set("website_url", "https://chromewebstore.google.com/example");
+
+  auto result = ExecuteToolAndWait(nav_tool, *base::WriteJson(input), false);
+  EXPECT_GT(result.size(), 0u);
+  EXPECT_THAT(result, ContentBlockText(testing::HasSubstr("Error")));
+
+  // Verify the page could not navigate to the URL
+  GURL final_url = web_contents()->GetURL();
+  EXPECT_EQ(initial_url, final_url);
+
+  // Also verify that other actions won't be able to execute against tabs
+  // already on an extension store URL.
+  base::test::TestFuture<actor::MayActOnUrlBlockReason> allowed;
+  auto* actor_service =
+      actor::ActorKeyedServiceFactory::GetActorKeyedService(agent_profile_);
+  actor_service->GetPolicyChecker().MayActOnUrl(
+      GURL("https://chromewebstore.google.com/example"), false, agent_profile_,
+      actor_service->GetJournal(), actor::TaskId(), allowed.GetCallback());
+  EXPECT_NE(allowed.Take(), actor::MayActOnUrlBlockReason::kAllowed);
+}
+
 // Test drag and release tool with coordinates (since drag needs from/to)
 IN_PROC_BROWSER_TEST_F(ContentAgentToolsTest,
                        DragAndReleaseTool_CoordinateTargets) {
diff --git a/chromium_src/chrome/browser/actor/site_policy.cc b/chromium_src/chrome/browser/actor/site_policy.cc
new file mode 100644
index 00000000000..490141b743c
--- /dev/null
+++ b/chromium_src/chrome/browser/actor/site_policy.cc
@@ -0,0 +1,34 @@
+// Copyright (c) 2025 The Brave Authors. All rights reserved.
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#include "extensions/buildflags/buildflags.h"
+#if BUILDFLAG(ENABLE_EXTENSIONS)
+#include "extensions/common/extension_urls.h"
+#endif
+
+namespace {
+
+bool IsChromeWebStoreURL(const GURL& url) {
+#if BUILDFLAG(ENABLE_EXTENSIONS)
+  return (url.GetHost() == extension_urls::GetWebstoreLaunchURL().GetHost()) ||
+         (url.GetHost() == extension_urls::GetNewWebstoreLaunchURL().GetHost());
+#else
+  return false;
+#endif
+}
+
+}  // namespace
+
+// Add Brave-specific restrictions
+#define BRAVE_MAY_ACT_ON_URL_INTERNAL                       \
+  if (IsChromeWebStoreURL(url)) {                           \
+    decision_wrapper->Reject(                               \
+        "Extension store URL",                              \
+        actor::MayActOnUrlBlockReason::kUrlNotInAllowlist); \
+    return;                                                 \
+  }
+
+#include <chrome/browser/actor/site_policy.cc>
+#undef BRAVE_MAY_ACT_ON_URL_INTERNAL
diff --git a/patches/chrome-browser-actor-site_policy.cc.patch b/patches/chrome-browser-actor-site_policy.cc.patch
new file mode 100644
index 00000000000..e2e00234327
--- /dev/null
+++ b/patches/chrome-browser-actor-site_policy.cc.patch
@@ -0,0 +1,12 @@
+diff --git a/chrome/browser/actor/site_policy.cc b/chrome/browser/actor/site_policy.cc
+index e4dc851408f20fbc02d06110c10f441a3e77c79c..b5a670ac861c6c7840877ca8260f5f45b44d49fc 100644
+--- a/chrome/browser/actor/site_policy.cc
++++ b/chrome/browser/actor/site_policy.cc
+@@ -169,6 +169,7 @@ void MayActOnUrlInternal(
+     return;
+   }
+ 
++  BRAVE_MAY_ACT_ON_URL_INTERNAL
+   if (DisableSafetyChecks()) {
+     decision_wrapper->Accept();
+     return;