Hello Xenforo forums!

So I am a member on a big forum and we review people's websites and tell them good and bad things. Occasionally, if they use Xenforo, we ask them for their API Key to verify they didn't pirate Xenforo. Though, I just found this one member that refuses to give up his API Key and I want to know how and where I can report it to Xenforo officials.
Here is his website URL: