The challenge told us on #hacklu-saloon @ there was a bot which has some nice features to try. You can send some commands like !help, !request, !base64, !rot13 etc.. but most of them were pretty much useless. One of them, !status, report us the list of channels the bot joined and in the list there were a nice one: #hacklu-secret-channel. Sadly the channel mode was +i so we need an invitation to join. After struggling for some time we came up with the idea that we could exploit base64 decoding feature to inject some IRC command in the response like:

\r\nINVITE Razor4x #hacklu-secret-channel

By trying this: !base64d DQpJTlZJVEUgUmF6b3I0eCAjaGFja2x1LXNlY3JldC1jaGFubmVs

an IRC message came up:

* You have been invited to #hacklu-secret-channel by barmixer-bot (

So now just join the secret channel and grab the flag:

FLAG: GfeBNmN5XjwDvQB64qoqaEEeYogk4rGH3ikZ0qtc3B3HKLDoAH