The PHP.net site has posted the official announcement about the latest release in the PHP 5.6.x series: PHP 5.6.28:

The PHP development team announces the immediate availability of PHP 5.6.28. This is a security release. Several security bugs were fixed in this release. All PHP 5.6 users are encouraged to upgrade to this version.

Fixes included in this release relate to:

• core language functionality
• GD image manipulation
• fixing an overflow in the IMAP functionality
• a SQLite issue fetching an integer as a string

As always, you can get this latest release from either the main downloads page (for source packages) or windows.php.net for the Windows binaries. As a reminder, the active support for the PHP 5.6.x series will be ending at the end of 2016 (December 31st) so there's never been a better time to upgrade to PHP 7.