It does make you wonder; how does a bug like this come to be?
We forgot to ban the new christmas ornament (firebomb clone) in duels. To save server hosting costs, duels are actually larger playercount servers, where players are on the same map, but don't see/interact with eachother. The instancing logic for the fire bombs was never implemented, because they are banned in duels (along with some other equipment), so they end up burning everyone on the server. Hotfix should be out in a few hours.