Hi! I have very strange problem! I have 2 sites with one (admin) account.
On ich one Annonimous users can not create any account, but somehow there are plenty new users!
I change my passwords on Drupal site and on server but it is happening again!!!
Today I deleted about 25 accounts and after 30 minutes new were created!
I disable all dev modules, clean cache and run updates.
here is one of my sites: creartive. pl