A flaw was found in X.Org Server Overlay Window. A Use-After-Free may lead to local privilege escalation. If a client explicitly destroys the compositor overlay window (aka COW), the Xserver would leave a dangling pointer to that window in the CompScreen structure, which will trigger a use-after-free later.
https://www.openwall.com/lists/oss-security/2023/03/29/1
https://security.gentoo.org/glsa/202305-30
https://gitlab.freedesktop.org/xorg/xserver/-/commit/26ef545b3502f61ca722a7a3373507e88ef64110