    private function sendString($string)
    {
        if ($this->pop_conn) {
            if ($this->do_debug >= 2) { //Show client messages when debug >= 2
                echo "Client -> Server: $string";
            }
            return fwrite($this->pop_conn, $string, strlen($string));
        }
        return 0;
    }
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.