Apache2 update 2.2.22-13 deb7u1 breaking WordPress

Hi,
I have a TurnKey WordPress VM. It is in multi-domain mode and has been working fine until I install the latest Apache2 update 2.2.22-13+deb7u1. When that is installed all of my pages display something along the lines of this:

<?php
/**
 * Front to the WordPress application. This file doesn't do anything, but loads
 * wp-blog-header.php which does and tells WordPress to load the theme.
 *
 * @package WordPress
 */

/**
 * Tells WordPress to load the WordPress theme and output it.
 *
 * @var bool
 */
define('WP_USE_THEMES', true);

/** Loads the WordPress Environment and Template */
require( dirname( __FILE__ ) . '/wp-blog-header.php' );

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Any ideas? All of my plugins are up to date.