This release [of PHP 5.5.13] fixes several bugs in PHP 5.5.12, and addresses two CVEs in Fileinfo (CVE-2014-0238 and CVE-2014-0237). [Additionally, in PHP 5.4.29] 16 bugs were fixed in this release, including two security issues in fileinfo extension. All PHP 5.4 users are encouraged to upgrade to this version. [...] All PHP users are encouraged to upgrade to these new versions.
As always, you can get these latest releases from either the main downloads page or windows.php.net for the Windows users out there. For the complete list of changes in either release, see the full Changelog.