Power Management in Apple Mac OS X before 10.8.5 does not properly perform locking upon occurrences of a power assertion, which allows physically proximate attackers to bypass intended access restrictions by visiting an unattended workstation on which a locking failure had prevented the startup of the screen saver.
Apple Security Advisory 2013-09-12-1 - OS X Mountain Lion v10.8.5 and Security Update 2013-004 is now available and addresses Apache issues, BIND issues, ClamAV issues, and more.