    public function checkNeeded($config) {
        $def = $config->getHTMLDefinition();
        foreach ($this->needed as $element => $attributes) {
            if (is_int($element)) $element = $attributes;
            if (!isset($def->info[$element])) return $element;
            if (!is_array($attributes)) continue;
            foreach ($attributes as $name) {
                if (!isset($def->info[$element]->attr[$name])) return "$element.$name";
            }
        }
        return false;
    }
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.