[Alfa1]

When you are on any page with the chatbox active, just type this in the browser address bar:
javascript:display_channel(1);

Change the number around to go to other channels.

I tested this in FF latest version.

The current functionality only adds a button to a channel. The only thing that stops someone from entering a restricted channel is that the button is gone. The code to go to the channel still works, as there are no permission checks for the function.