The bug has been a . On January 1, Google engineer Michal Zalewski , along with some technical details, saying that he was concerned that Chinese hackers may have already discovered the problem. He said that he warned Microsoft about the flaw back in July. Microsoft maintains that it was unable to reproduce the problem until December.

Google isn't saying who exactly was targeted in this latest incident, but Chinese activist groups have been the focus of cyber attacks in the past. This may be another example of an ongoing and methodical effort to track and steal information from pro-democracy and Tibetan activists.

Zalewski referred an inquiry to Google's public relations team, which declined to comment further on the matter.

Now that the flaw is being exploited in attacks, the pressure is mounting on Microsoft to produce a reliable patch for the issue that can be pushed out to hundreds of millions of customers.

"For now, we recommend concerned users and corporations seriously consider deploying Microsoft's temporary Fixit to block this attack until an official patch is available," Google said.