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://exchange.xforce.ibmcloud.com/vulnerabilities/48727
http://www.vupen.com/english/advisories/2009/0422
http://support.apple.com/kb/HT3438
http://lists.apple.com/archives/security-announce/2009/Feb/msg00000.html