If you woke up this morning to your machine telling you that a new build of Windows 10 is ready to install, you might want to hold off on downloading the update. Microsoft has accidentally released a new build of Windows 10 and it looks like it is going to all rings of the Insider program.
The build, 18947, appears to be pushed to Insiders on Fast and Slow rings for both x86 and x64 flavors; meaning nearly everyone is getting this release. This version of Windows 10 is from the canary branch and appears to be only about a day or so old.
Microsoft is aware of the issue and is looking into the release but know that unless you like to really live on the dangerous side of life, you are better off not installing this update. That being said, seeing as this release was not intended for public consumption (at least, when it was published) it may also contain hidden features that have yet to be announced.
Users on the Insider rings know the risks of running pre-release updates, an accidental release of a build to all rings is a serious issue for Microsoft, but installing this build comes with even more risk than typical for the program. The company does try to hold back releases that will corrupt machines in the preview program but this release has slipped through without the proper telemetry to know if there are any major issues.