Microsoft usually releases security fixes for its software, including the Windows operating system, on Patch Tuesday, but this time the company might have to move a bit faster because of a vulnerability that has been made public by a Google security engineer.

A Google researcher named forshaw found a critical security flaw in Windows 8.1 that would allow an attacker to get administrator privileges on any system, and at this point, there’s absolutely no workaround or patch available to address this issue.

forshaw has also posted a Proof of Concept (which you can read in full in the box after the jump) that demonstrates the vulnerability, pointing out that he’s not sure whether the same bug exists in Windows 7 or any other Windows version.

Microsoft knew about this issue

Even though some criticized forshaw for making this vulnerability public, it’s worth mentioning that Microsoft was contacted by the Google engineer soon after finding it in September 2014 as part of the Google Project Zero research program.

His post is dated September 30, and given the fact that Google Project Zero has a 90-day disclosure policy, the initial report went public, urging Microsoft to provide a patch for affected systems.

At this point, it’s not yet clear whether Microsoft is planning to wait until this month’s Patch Tuesday or release an out-of-band fix in the coming days. The January 2015 Patch Tuesday rollout takes place on January 13.

Bug confirmed, fix on its way

In a statement we received this morning, Microsoft confirms the issue and says that it’s already working on a fix.

Even though there’s no workaround available at this point, the company says that Windows users should keep anti-virus protection turned on all the time and enable firewalls to make sure that no exploits are being used against their computers.

Here is the official statement provided by Microsoft, and scroll down to read the whole advisory released by the Google security engineer.

“We are working to release a security update to address an Elevation of Privilege issue. It is important to note that for a would-be attacker to potentially exploit a system, they would first need to have valid logon credentials and be able to log on locally to a targeted machine. We encourage customers to keep their anti-virus software up to date, install all available Security Updates and enable the firewall on their computer.”

Updated on January 2, 2015 to state that there's no patch available at the time of posting the article and all Windows 8.1 systems are vulnerable. There's still no indication if other Windows versions are affected.