    public function destroy($name) {
        if (!isset($this->_storage[$name])) {
            trigger_error("Attempted to destroy non-existent variable $name",
                          E_USER_ERROR);
            return;
        }
        unset($this->_storage[$name]);
    }
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.