This happened before the forum software switch, and I'm not sure it was ever disclosed. However, this is a good time to remind everyone about password security and why you should never re-use a password for two different websites.
https://www.troyhunt.com/i-just-added-another-140-data-breaches-to-have-i-been-pwned/
Look down on line #12. Your password from here at that time is out there for sale on the internet, and people have it.
Change your password now if you haven't already, on every website you even think you might have used it on.
ETA: Your password was stored as a salted and encrypted hash, not clear text. But, it's only math, and the algorithm for vBulletin is very well known.
https://www.troyhunt.com/i-just-added-another-140-data-breaches-to-have-i-been-pwned/
Look down on line #12. Your password from here at that time is out there for sale on the internet, and people have it.
Change your password now if you haven't already, on every website you even think you might have used it on.
ETA: Your password was stored as a salted and encrypted hash, not clear text. But, it's only math, and the algorithm for vBulletin is very well known.