XTerm in Apple Mac OS X 10.4.11 and 10.5.6, when used with luit, creates tty devices with insecure world-writable permissions, which allows local users to write to the Xterm of another user.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2009-0150
http://www.vupen.com/english/advisories/2009/0422
http://www.securityfocus.com/bid/33798
http://securitytracker.com/alerts/2009/Feb/1021729.html
http://secunia.com/advisories/33937
http://lists.apple.com/archives/security-announce/2009/Feb/msg00000.html