register as admin

Hi,

I just noticed a user (WoodrowDouglass71) registered by himself and having the role of Administrator.

This user was created sept 2009 (shame on me to notice only now), and I don’t remember which version I was running by this time. Maybe 2.7.
When I updated to 2.9.2 (4 months ago) I disabled the “register” function so I think this hack or the likes do not apply any more to my wordpress blog.

Do you have any advice? should I check something? I can’t imagine what he could have done with such access I didn’t notice in 1 year.

Here is the tip he used, his first name was :

[Hack code moderated]

Thank you