On Zyxel models NBG6818, NBG7815, WSQ20, WSQ50, WSQ60, and WSR30, the UART port on the PCB board gives a root BusyBox shell that prompts for a non-user configurable hardcoded default password present in a configuration file on the firmware (/etc/uci_defconfig/system): /etc/uci_defconfig/system: option pwd "nbg6818@2019" option gui_pwd "1234" option language "en"