Well, I couldn't find anything related to an exploit that would explain this happening, and some details point to a bug actually.
And though we're not running the latest version of vB, I don't think that's the problem. The reported vB XSS exploit is not related to what I can see happened here.
Nevertheless I'll upgrade the forum again soon.
Finally, I see no evidence of any accounts being hacked as in, someone was able to login with your account and obtain any details you have stored. In fact, forum account details are minimal anyway and most, if not all of the details you enter here in the user control panel are publically visible anyway.
Your real account details and license if you have one have always been 100% safe as well, since those are stored in a whole other database on another server.
I hope that puts some minds at ease,