public function check_request($mode = rcube_utils::INPUT_POST)
    {
        // check secure token in URL if enabled
        if ($token = $this->get_secure_url_token()) {
            foreach (explode('/', preg_replace('/[?#&].*$/', '', $_SERVER['REQUEST_URI'])) as $tok) {
                if ($tok == $token) {
                    return true;
                }
            }

            $this->request_status = self::REQUEST_ERROR_URL;

            return false;
        }

        $sess_tok = $this->get_request_token();

        // ajax requests
        if (rcube_utils::request_header('X-Roundcube-Request') === $sess_tok) {
            return true;
        }

        // skip empty requests
        if (($mode == rcube_utils::INPUT_POST && empty($_POST))
            || ($mode == rcube_utils::INPUT_GET && empty($_GET))
        ) {
            return true;
        }

        // default method of securing requests
        $token   = rcube_utils::get_input_value('_token', $mode);
        $sess_id = $_COOKIE[ini_get('session.name')];

        if (empty($sess_id) || $token !== $sess_tok) {
            $this->request_status = self::REQUEST_ERROR_TOKEN;
            return false;
        }

        return true;
    }