Versions mentioned in the description apply to the upstream
Remediation section below for
Debian:10 relevant versions.
The authentication setup in XWayland 1.16.x and 1.17.x before 1.17.2 starts the server in non-authenticating mode, which allows local users to read from or send information to arbitrary X11 clients via vectors involving a UNIX socket.
xorg-server to version 2:1.17.2-1 or higher.