Multiple unspecified vulnerabilities in Safari RSS in Apple Mac OS X 10.4.11 and 10.5.6, and Windows XP and Vista, allow remote attackers to execute arbitrary JavaScript in the local security zone via a crafted feed: URL, related to "input validation issues."
http://support.apple.com/kb/HT3438
http://lists.apple.com/archives/security-announce/2009/Feb/msg00001.html
http://lists.apple.com/archives/security-announce/2009/Feb/msg00000.html