That's correct, only master password can change password, or add others to base if I'm right from what I remember. What I was thinking might have happened, done it myself before a few times. When entering password I forgot to add backslash "/" and it went straight into system chat, so if anyone is there they can see the base password just posted.
But even if that happened, somebody got it and docked with base and set-up a secondary base account (not a master pass one) to use later also. Don't think they can withdraw cash with that lesser base account, not sure now?
