Read the original article: Backdoor account discovered in more than 100,000 Zyxel firewalls, VPN gateways
The username and password (zyfwp/PrOw!aN_fXp) were visible in one of the Zyxel firmware binaries.
Read the original article: Backdoor account discovered in more than 100,000 Zyxel firewalls, VPN gateways