It's just speculation that someone used GM powers to do this. Most likely they tracked down a boss mass wipe ability (i.e. kills all players within 30 yards) th

It's just speculation that someone used GM powers to do this. Most likely they tracked down a boss mass wipe ability (i.e. kills all players within 30 yards) that was incorrectly flagged as useable by players. You can then write an AddOn that uses CastSpellByID() to give you that ability. The GM interface requires a special build of the WoW client, a specially flagged account, and a two factor auth token to login. It's pretty hard to emulate the client as opcodes are randomly shuffled based on the hash of the binary itself.