When you're logged in the admin interface, it's possible to enter a url which will create a new class.

Steps to reproduce

If you log in to the admin interface and just enter a bogus url like:

/class/edit/bogus/(language)/eng-GB

You'll automatically create a new class.

This class will also be lost in the database, since it's no information related to any classgroup (In the table ezcontentclass_classgroup, you'll get group_id = 0 and a emty string in group_name).

Solution: Check post variables before any contentclass should be created.