    public function postFilter($html, $config, $context) {
        $post_regex = '#<span class="youtube-embed">((?:v|cp)/[A-Za-z0-9\-_=]+)</span>#';
        return preg_replace_callback($post_regex, array($this, 'postFilterCallback'), $html);
    }
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.