    public function addBlankElement($element) {
        if (!isset($this->info[$element])) {
            $this->elements[] = $element;
            $this->info[$element] = new HTMLPurifier_ElementDef();
            $this->info[$element]->standalone = false;
        } else {
            trigger_error("Definition for $element already exists in module, cannot redefine");
        }
        return $this->info[$element];
    }
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.