Windows 8.1's RTM, which Microsoft announced on Tuesday, has leaked to file-sharing sites, according to numerous forum postings and blog reports.

Leaks of unreleased Microsoft products, especially Windows, are commonplace, and as in this case, often occur just hours or days after the Redmond, Wash. company ships code to its partners.

Microsoft may have contributed to the interest in Windows 8.1 RTM -- a term that represents "release to manufacturers" -- because of a change in a long-standing policy that gave developers and IT professionals access to the official code weeks before the general public.

The leaked builds of Windows 8.1 RTM may have originated in China -- home of most of the companies that build the world's personal computers and tablets -- because a Chinese-language edition was the first to appear.

Within a short time, however, English editions of the RTM also popped up on file-sharing websites.

While at one time Microsoft tried to stamp out such leaks, it long ago gave up and switched to warning users that unauthorized builds, including counterfeits circulating long after a product's release, often contained malware.

Microsoft will officially launch Windows 8.1 on Oct. 17 in the U.S., the first date that current Windows 8 users can retrieve the free update from the Windows Store. Hardware that relies on Windows 8.1, as well as retail copies of the operating system, will go on sale Oct. 18.