Apple today released Security Update 2011-005 (Lion) and Security Update 2011-005 (Snow Leopard) which are both recommended for all users and improves the security of Mac OS X.
Both updates are available via Software Update and also as standalone installers.
More info and download links:
• Security Update 2011-005 (Lion)
• Security Update 2011-005 (Snow Leopard)
For information on the security content of this update, please visit this website: http://support.apple.com/kb/HT1222