    static public function make($s) {
        if ($s instanceof HTMLPurifier_Length) return $s;
        $n_length = strspn($s, '1234567890.+-');
        $n = substr($s, 0, $n_length);
        $unit = substr($s, $n_length);
        if ($unit === '') $unit = false;
        return new HTMLPurifier_Length($n, $unit);
    }
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.