rxvt-unicode 9.22, rxvt 2.7.10, mrxvt 0.5.4, and Eterm 0.9.7 allow (potentially remote) code execution because of improper handling of certain escape sequences (ESC G Q). A response is terminated by a newline.
https://www.openwall.com/lists/oss-security/2021/05/17/1
https://www.openwall.com/lists/oss-security/2017/05/01/20
https://sourceforge.net/projects/rxvt/files/rxvt-dev/
https://sourceforge.net/projects/materm/files/mrxvt%20source/
https://security.gentoo.org/glsa/202209-07
https://security.gentoo.org/glsa/202105-17
https://packetstormsecurity.com/files/162621/rxvt-2.7.0-rxvt-unicode-9.22-Code-Execution.html
https://lists.debian.org/debian-lts-announce/2021/06/msg00012.html
https://lists.debian.org/debian-lts-announce/2021/06/msg00011.html
https://lists.debian.org/debian-lts-announce/2021/06/msg00010.html
https://lists.debian.org/debian-lts-announce/2021/05/msg00026.html
https://git.enlightenment.org/apps/eterm.git/log/
http://cvs.schmorp.de/rxvt-unicode/src/command.C?r1=1.582&r2=1.583