Did you ever have a UBB.classic on your server? Is it still there?
Because I'm thinking this person maybe found an old UBB.classic and can read it in plain text because .cgi isn't being processed anymore?
Which means the members files are going to show in plain text.
Which means I hope your password isn't the same anymore.
That's all if you actually had a UBB.classic and it's still laying around, broken. If not, there's nothing to worry about at all, you're being bluffed.