The PHP development team released 5.3.9, it is an improvement on the stability and contains some security fixes. I’ve successfully tested it on my servers without a noticeable problem.

Security Enhancements and Fixes in PHP 5.3.9:

• Added max_input_vars directive to prevent attacks based on hash collisions. (CVE-2011-4885)
• Fixed bug #60150 (Integer overflow during the parsing of invalid exif header). (CVE-2011-4566)

Key enhancements in PHP 5.3.9 include:

• Fixed bug #55475 (is_a() triggers autoloader, new optional 3rd argument to is_a and is_subclass_of).
• Fixed bug #55609 (mysqlnd cannot be built shared)
• Many changes to the FPM SAPI module

To see the buglist solved in this release, read them in the ChangeLog.

For instructions on how to upgrade PHP please read: Upgrading PHP.