From 9ec61d5e14fff874426e560d593f93094c4377b7 Mon Sep 17 00:00:00 2001
From: Tom Anderson <thomasanderson@chromium.org>
Date: Wed, 12 Aug 2026 14:40:10 -0700
Subject: [PATCH] [ui/gtk] Pin gtk-modules to an empty string during initialization

Setting `gtk-modules` to `""` in GtkUi::Initialize() assigns
GTK_SETTINGS_SOURCE_APPLICATION priority to the setting, preventing
lower-priority XSETTINGS updates from overriding `gtk-modules` and
executing untrusted GTK modules in the unsandboxed browser process via a
retained X11 connection.

Fixed: 545124048
Change-Id: I91e1c3df94c0567c69eec676da26ee1bb46eca2f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8243490
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1678319}
---

diff --git a/ui/gtk/gtk_ui.cc b/ui/gtk/gtk_ui.cc
index 68df09b..a688787 100644
--- a/ui/gtk/gtk_ui.cc
+++ b/ui/gtk/gtk_ui.cc
@@ -365,6 +365,9 @@
   };
 
   GtkSettings* settings = gtk_settings_get_default();
+  // Pin `gtk-modules` to an empty string with APPLICATION source priority
+  // to prevent XSETTINGS updates from loading GTK modules.
+  g_object_set(settings, "gtk-modules", "", nullptr);
   SanitizeIconThemeName();
   SanitizeThemeName();
   InstallGtkSettingsInterceptor();