Account reset requests are on their way to the affected parties.
"There's been a recent increase in unauthorized World of Warcraft account logins via our website and the World of Warcraft mobile armory app," says Blizzard, as it shuts down the mobile auction house app temporarily. Those whose accounts have been showing signs of unauthorized access - unusual IP addresses, plus lack of an authenticator - have already been sent account reset requests. There's no word on how long the mobile auction house will be down, but customer support will be helping anyone whose in-game items and gold have been affected.
This issue was first reported by WoW Insider, when people started complaining that their mobile armory accounts were being hacked. The hackers were accessing those accounts, and immediately using them to spent vast sums at the Auction House for worthless items. "I felt my phone vibrate so I took it out to see what it was," said one affected user on the Battle.net forums. "Somehow, magically my Mobile Armory app had been opened and as I tried to swap toons on my WoW account, it prevented me from logging in because my mobile armory was logging in."
Blizzard acknowledges that no method of account security is guaranteed. It asks every user to take all possible precautions to secure their machines; even changing the password periodically "adds another defensive barrier."