Apple Safari before 4.0.5 on Windows does not properly validate external URL schemes, which allows remote attackers to open local files and execute arbitrary code via a crafted HTML document.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A6817
http://www.securitytracker.com/id?1023706
http://www.securityfocus.com/bid/38671
http://support.apple.com/kb/HT4070
http://lists.apple.com/archives/security-announce/2010/Mar/msg00000.html