Apple has released Mac OS X 10.8.5 and Security Update 2013-004. Each of these fixes a large number of critical vulnerabilities in Mac OS X and Mac OS X Server, the most serious of which may lead to unexpected application termination or arbitrary code execution. For more information, see http://support.apple.com/kb/HT5880
Mac OS X 10.8.5 update is available for Mac OS X 10.8.x and Mac OS X Server 10.8.x.
Security Update 2013-004 is available for Mac OS X 10.7.5, Mac OS X Server 10.7.5, Mac OS X 10.6.8 and Mac OS X Server 10.6.8.
Software Update will install either Mac OS X 10.8.5 or Security Update 2013-004, whichever is appropriate for your system.