Windows 10 for PCs build 14278 leaked onto the Internet today. If we"re going by build numbers, the leaked build is actually older than the current Fast ring build.
Of course, this is an RS1 build, so we know there are more features coming and there could have been more features in builds that were exclusively for internal testing. Early reports are that there"s not much that"s new.
We"ll know more when we get the build installed on our machines, but we stress that we do this so you don"t have to. We do not recommend installing a leaked build on your machine.
Microsoft will announce more about what"s coming in the Redstone update at Build in a few weeks. As of right now, there haven"t been any major features in the Insider Previews.