Apple has released Mac OS X v10.6.8 and Security Update 2011-004 addressing a total of 39 vulnerabilities in OS X 10.5.x and 10.6.x.
Many are critical errors which could allow an attacker to take control of the system!
Please use the System Update. You can read the notice here:
And get the direct download here:
As usual I would remind you to also make sure you also update your Web Browser(s) and plug ins – ESPECIALLY Adobe Flash and Adobe Acrobat!