I had to clean a child porn image once because some bastard registered at an instance I’m moderating and posted an anime child porn image to another instance using the account he created here. And I found a total of 5 copies of that image in the server…
I actually screwed up twice on dev environment. Luckily the second case was salvageable without using data from an old backup(I wasn’t given one that time) and I managed to sweep it up fast.
I started testing my queries super carefully after the first incident, but I was too tired once that I forgot to restrict the update scope for testing and screwed up again.