Want to get an advance look at what Microsoft has cooking in the first big update to Windows 8.1? You're in luck: The update is now available online, but not from Microsoft.

Several file locker sites now host the Windows 8.1 Update 1, thanks to an apparently accidental leak from Microsoft's servers. The company put the update on its public Windows Update servers so company employees could get the update, but it kept outsiders in the dark by labeling the files with non-obvious file names. However, with a simple software tweak, many were able to fool the servers into thinking they were Microsoft employees, letting them obtain the files.

See also: The Problem With Windows 8

Although Microsoft has since patched the security hole, the damage was already done. Copies of the update now reside on public file lockers, such as Mega, letting anyone download and install the software.

Windows 8.1 Update 1 isn't yet officially supported by Microsoft. Although the company issued the release to manufacturing (RTM) version on Wednesday, which represents the final version of the software before release, some hardware-specific drivers and links to as-yet-updated services may not work. If you're thinking about installing it, proceed with extreme caution.

The update contains some notable updates to the Windows modern (aka Metro) interface. The desktop's task bar can now appear in the Modern environment and the Start screen, and Modern apps appear in it. There's also a permanent shutdown button on the Start screen. As rumored, the update also boots right into the Desktop on any device not equipped with a touchscreen.

The UI changes follow the same general trend as previous updates. The traditional Windows desktop is reasserting itself as the cries against the Modern environment have grown louder and PC sales have continued to decline. Microsoft is changing Windows to appease users hesitant to make the jump to Windows 8.1, while trying not to undermine its own vision of touch and tablet computing.

Microsoft is expected to release the official update to the public on April 8. At the same time, it's also expected to launch a version of Windows 8.1 supported by Bing and other services that will be free for non-Windows 8/8.1 users.