Cross-site scripting (XSS) vulnerability in WebKit in Apple Safari before 5.0.6 allows remote attackers to inject arbitrary web script or HTML via vectors involving a URL that contains a username.
http://support.apple.com/kb/HT4999
http://support.apple.com/kb/HT4808
http://lists.apple.com/archives/security-announce/2011//Jul/msg00002.html
http://lists.apple.com/archives/Security-announce/2011//Oct/msg00001.html