    public function get($name) {
        if ($this->has($name)) return $this->data[$name];
        // possible performance bottleneck, convert to iterative if necessary
        if ($this->parent) return $this->parent->get($name);
        throw new HTMLPurifier_Exception("Key '$name' not found");
    }
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.