selabel_x(5) on Linux
The text 7139f7274650, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it. The page shows this text now.
userspace SELinux labeling interface and configuration file format for the X Window System contexts backend. This backend is also used to determine the default context for labeling remotely connected X clients