The PHP development team announces the immediate availability of [these PHP versions]. Five security-related issues in PHP were fixed in this release, including CVE-2015-3152. All PHP 5.6 users are encouraged to upgrade to this version.
One note here too - 5.5.27 is the last official bugfix release according to the release calendar for that major version. Upgrading to PHP 5.6 is encouraged (the next supported version). As always you can grab these latest downloads from the main downloads page (or windows.php.net) and see the full list of changes in the Changelog for each version.