Have I been hacked?

Am I supposed to have a registered user with the email address: [email protected]? Our site was recently hacked, and we had it cleaned out but we received a registration form from a strange email, and then today I noticed we had a new user named “admin” with the email address being [email protected] and I just want to see if everyone else has this user, or it was whoever created the account under our registration form and then they changed the email address (which I’ve since then turned off the ability for anyone else to register).

Thanks,