Administrator table contains registered user
 

I thought I would have a look at my tables and when I opened the Administrator table there was myself (naturally as I am the Administrator) but there was also a record for a standard registered user in there.

Looking at that user's details they are in the "Registered Users" usergroup.

My site requires phone numbers when registering so I phoned the person up and he was just an average person that used the site for a couple of months and hasn't been back - his user details confirms that he registered Dec 08 and last login was Jan 09

Has anyone else found this type of abnormality?