IOGraphics in Apple Mac OS X through 10.6.8 does not properly handle a locked-screen state in display sleep mode for an Apple Cinema Display, which allows physically proximate attackers to bypass the password requirement via unspecified vectors.
http://www.securityfocus.com/bid/50085
http://support.apple.com/kb/HT5002
http://lists.apple.com/archives/Security-announce/2011//Oct/msg00003.html