The latest version in the PHP 5.2.x series has been released - PHP 5.2.9 - with several bug and stability fixes. From the announcement:

The PHP development team would like to announce the immediate availability of PHP 5.2.9. This release focuses on improving the stability of the PHP 5.2.x branch with over 50 bug fixes, several of which are security related.All users of PHP are encouraged to upgrade to this release.

Four security enhancements/fixes are specifically mentioned - a problem with imagerotate, a crash that can happen when extracting zip files, a problem with explode and empty strings and a segfault in json_decode. The full Changelog is here.

You can get the latest download from the downloads page on the PHP.net site (or your favorite mirror).