xdg-dbus-proxy before version 0.1.2-3.oe2403sp3 contains a vulnerability where an attacker can bypass message filtering on the D-Bus session bus by setting a reply serial number on non-reply messages. This flaw allows a malicious or compromised Flatpak application to potentially execute arbitrary code outside its sandbox. The issue arises from incorrect message filtering implementation. A fix is available in version 0.1.2-3.oe2403sp3.