    protected function listifyTagLookup($array) {
        ksort($array);
        $list = array();
        foreach ($array as $name => $discard) {
            if ($name !== '#PCDATA' && !isset($this->def->info[$name])) continue;
            $list[] = $name;
        }
        return $this->listify($list);
    }
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.