Source: xorg Severity: normal Dear Maintainer,
it seems that the X server SECURITY extension is not enabled / supported by default. This extension is necessary for clients connecting via ssh -X to a server, i.e. via untrusted ssh X forwarding. While debian patches ssh to disable untrusted ssh X forwarding (i.e. ssh -X is equivalent to ssh -Y), this is not true for all other distributions. This results in X forwarding to fail when connecting from a machine that uses the unpatched / upstream ssh client. The SECURITY extension can be enabled via the --enable-xcsecurity build flag. See also https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=221984 -- System Information: Debian Release: 9.1 APT prefers stable APT policy: (1000, 'stable'), (990, 'stable') Architecture: amd64 (x86_64) Locale: LANG=en_US.UTF-8, LC_CTYPE=zh_CN.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Init: systemd (via /run/systemd/system)