Accounts being compromised?

My server got closed for no reason, and one of my other servers that I don't use anymore was opened with 3 random people (I got their names). I randomly got logged out and my server turned into craftbucket 1.7.2, when I never set it to that in the first place. I got logged out again after that. I just joined the server where the 3 people were, and nobodys in it, and there was a random wood tower, and just now my other server got changed to vanilla 1.7.2.