The Zyxel P2000W (Version1) VoIP Wifi phone allows for unauthenticated access to data and has hardcoded DNS servers.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/41681/ZyxelVOIP.txt
Source: https://packetstormsecurity.com/files/41681/ZyxelVOIP.txt.html