Plesk allows username 'root' for MySQL databases.

[Tozz]

There is a minor bug in Parallels Plesk (tested with 11.5) where regular users are allowed to create MySQL accounts with username 'root'. Obviously this account does not work, but no error is given by Plesk causing the customer to think he has done everything correctly.

I feel certain usernames should be forbidden by default, such as 'root', 'admin', 'psa' and perhaps MySQL reserved words.