The screen saver in Dock in Apple Mac OS X 10.5 before 10.5.8 does not prevent four-finger Multi-Touch gestures, which allows physically proximate attackers to bypass locking and "manage applications or use Expose" via unspecified vectors.
https://exchange.xforce.ibmcloud.com/vulnerabilities/52421
http://www.vupen.com/english/advisories/2009/2172
http://www.us-cert.gov/cas/techalerts/TA09-218A.html
http://www.securityfocus.com/bid/35954
http://support.apple.com/kb/HT3757
http://secunia.com/advisories/36096
http://lists.apple.com/archives/security-announce/2009/Aug/msg00001.html