World of Warcraft developer Blizzard Entertainment recently acknowledged that an "in-game exploit" had caused the deaths of both player characters and non-player characters in some of the game's major cities.

"Imagine logging into your favorite MMO only to find that a previously populated capital city is a barren wasteland devoid of life," writes Massively's Justin Olivetti. "This actually happened yesterday to some denizens of World of Warcraft, as mischief-makers used an exploit to kill everyone -- human players and NPCs alike -- in the biggest cities. Stormwind and Orgrimmar were completely wiped out on several servers, with other towns reportedly coming under nefarious attacks."

"Blizzard instantly formed a crack strike team to investigate what was now called the 'WoW apocalypse,' or the 'WoW mass murder hac,'" writes's Mark Hachman. "The obvious conclusion? Hackers."

"How did they do that? 'A kill hack,' explained one of the perpetrators on a forum I tracked down easily but probably shouldn't link to," writes's Robert Purchese. "'We didn't do any permanent damage,' the bringer of death retaliated. 'Some people liked it for a new topic of conversation and a funny stream to watch, and some people didn't. The people who didn't should be blaming Blizzard for not fixing it faster (four hours of obvious use is sad).'"

"The hackers' attack saw every character in cities such as Stormwind, Orgrimmar, Tarren Mill and Ragnaros killed off, leaving piles of skeletons cluttering the streets and buildings. According to the Blizzard, the vulnerability exploited by the hackers has now been patched," writes Sophos' Graham Cluley. "Blizzard is likely to ban the culprits if they manage to identify them, and could possibly take legal action if they can prove that financial losses occurred as a result of the hack."

"Around 10 million people worldwide pay subscription fees for the game including several million who have joined the most recent campaign, 'the fight for Pandaria,'" AFP reports. "Players represented by animated characters such as dwarfs, trolls, or humans explore, battle, and take on quests in the game made by Blizzard, a division of Activision."