    private function character($s, $l = 0) {
        if($s + $l < $this->EOF) {
            if($l === 0) {
                return $this->data[$s];
            } else {
                return substr($this->data, $s, $l);
            }
        }
    }
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.