Hey man, for over a month now there has been a notorious troll who has been hijacking groups by applying as a co-founder, deleting all the artwork, and replacing it with gore, scat, porn, racism and transphobia. If you are in any groups, tell them to set their admin permissions to "Subject to Vote" or "Are Not Allowed"
This should serve as a handy guide.
Also, I recommend joining or watching the NoMoreHackers group to keep track of the troll's newest accounts and the groups he has attacked. https://www.deviantart.com/nomorehackers