    public function getChildDef($def) {
        if ($def->content_model_type != 'strictblockquote') return parent::getChildDef($def);
        return new HTMLPurifier_ChildDef_StrictBlockquote($def->content_model);
    }
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.