Possible admin privileges exploit

I’ve decided to take a look at users registered on one of my webistes, and what I found:

link1
link1

Content of NAME field is:

[Script moderated]

I am not able to say if this account was maliciously created before I upgraded WP from 2.9.1 to 3.0.1 or after.
Just to let you know.
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edit: user was created at 2009-09-05 01:23:25, so before 3.0.1 – around 2.9. Anyway it’s worth of looking into.