The PHP development group has officially released the latest version of the PHP 5.4.x series today - PHP 5.4.18:

The PHP development team announces the immediate availability of PHP 5.4.18. About 30 bugs were fixed, including security issues CVE-2013-4113 and CVE-2013-4073. All users of PHP are encouraged to upgrade to this release.

The two security issues revolved around a denial of service involving XML parsing and problems with certificate handling. You can download this latest version from the usual places - the downloads page for the source release or the Windows site for binary downloads.If you're interested in the other 28 bugs fixed, you can check out the changelog.