Some interesting CGI commands (at least in the 1.00.04.c and 1.00.06 versions of the firmware):
To bypass firmware upgrade password for a ProvisionedDevice (tested on 1.00.04.c, 1.00.06 and 2.00.05):
Replace 192.168.15.1 with the IP address of your WRP400, and use the correct admin password if you've changed it from the default.
The TftpOn and TftpOff commands can be used to UnlockTheConsole. The Reboot and FactoryReset commands do what the names suggest.