PHP team has released a warning about their previous stable release: PHP 5.3.7. That version has a serious bug that affects crypt() function where it only returns the salt for MD5 where it should have returns the whole value.
To remedy this situation, a new version of PHP has been released and it's the recommended solution to fix the previous problems. This version only has two fixes, which is considerd the most important bug fixes that should be applied immediately.
If you haven't upgraded to 5.3.7 yet, it's the best time to upgrade to 5.3.8