You want a copy of Windows 8 Pro? Go ahead and download it -- Microsoft is giving the keys away for free.

According to VentureBeat, an interesting exploit on Microsoft's download page allows users to pick up a free copy of Windows 8 Pro -- directly from the website, and at no cost.

If you attempt to download the free Microsoft Windows Media Center upgrade, which is being offered until January 31, a strange side effect takes hold. Windows 8 Pro will be permanently activated.

Microsoft / Screenshot by CNET

For the pirates among us, this would provide a handy workaround for the tech giant's Key Management Service (KMS). Built for enterprise users, the KMS is intended to make deployment of Windows 8 through a KMS host and KMS client, making Windows 8 fully usable for 180 days before activation. In other words, instead of being required to input an activation key or reach Microsoft authentication channels on each individual computer, businesses can activate Windows copies on a local network and make the transition step-by-step.

Within the enterprise, making Windows deployment processes easier can only be a good thing. However, this does mean that by setting up pirate KMS servers, keys can be traded across the Internet for free.

One feather in Microsoft's cap, however, is that Windows has to be reactivated every 180 days using this method. Volume keys are no longer in use, and so each individual PC needs a unique key. Thus, "legitimate" activation cannot be achieved through multiple users activating through the same key.

As a result, pirates have had to come up with more complex methods, possible through the KMS system, but more time-consuming than simply downloading a Windows Media Center upgrade.

Once you've reached the desktop within the Windows 8 Pro installation and after applying a KMS key, using the new Windows Media Center upgrade key -- obtained for free by Microsoft's Web site -- does not result in a validity check. Therefore, any version of Windows 8 Pro, whether obtained through a pirate KMS network or not, will become fully active and "legitimate."

Stephen Hall at Windows Wave originally reported the exploit and was able to confirm that it works, at least for now.

Reddit user noveleven explained on a discussion thread why the method, in theory, works:

When you activate Windows via KMS, in the activation window it says "Windows is activated until..." and a date (so if you were to install it today, it would say it's activated until May). After installing the upgrade, the window just says "Windows was activated on..." and the date of activation. That means the activation is permanent. When you install the upgrade key, that replaces the existing product key; only the new upgrade key is used for future checks. Windows won't check the key you used to install because it no longer has it.

ZDNet has contacted Microsoft and will update the piece if we hear back.

This story originally posted as "Microsoft gives away Windows 8 Pro to pirates by accident" on ZDNet.