An in-game World of Warcraft exploit left entire cities dead last night, according to the Blizzard forums.
The exploit began on the European servers where level one characters were able to instantly kill everyone, wiping out the cities of Ogrimmar, Stormwind, Tarren Mill, Ragnaros, Draenor, Twisting Nether, and other realms in the US.
A Blizzard community manager posted to the game's forums today announcing that a hotfix for the exploit had been issued.
"Earlier today, certain realms were affected by an in-game exploit, resulting in the deaths of player characters and non-player characters in some of the major cities," the community manager wrote. "This exploit has already been hotfixed, so it should not be repeatable. It's safe to continue playing and adventuring in major cities and elsewhere in Azeroth.
"As with any exploit, we are taking this disruptive action very seriously and conducting a thorough investigation. If you have information relating to this incident, please email email@example.com. We apologize for the inconvenience some of you experienced as a result of this and appreciate your understanding."
The video below shows players in Stormwind being wiped out.