A bit of a moan, but I need some advice.

Currently https://openbenches.org allows *anyone* to upload a bench & photo without registration.

It has been mostly fine but yesterday an anonymous user added some stupid photos. Only the 4th time that's happened.

I wanted to restrict adding & editing to registered users. But today a GitHub user went in and deliberately vandalised one of the entries.

The users have been banned and the changes reverted.

Is there a realistic way to stop this?