This update removes the most common variants of the Flashback malware. If the Flashback malware is found, a dialog will notify you that malware was removed. In some cases, the update may need to restart your computer in order to completely remove the Flashback malware.
To improve the security of your Mac, this update also disables the Java plug-in in Safari. For instructions on how to re-enable it, please visit: http://support.apple.com/kb/HT5241.
See this article on how to verify the authenticity of this update.
For information on the security content of this update, please visit this website: http://support.apple.com/kb/HT1222.