CFNetwork in Apple Safari before 4.0 misinterprets downloaded image files as local HTML documents in unspecified circumstances, which allows remote attackers to execute arbitrary JavaScript code by placing it in an image file.
http://www.vupen.com/english/advisories/2009/1522
http://www.securityfocus.com/bid/35344
http://support.apple.com/kb/HT3613
http://securitytracker.com/id?1022343
http://secunia.com/advisories/35379
http://lists.apple.com/archives/security-announce/2009/jun/msg00002.html