Over the past weekend, Windows 10 Build 9901 got leaked on the web. This build included several new UI changes, Cortana and new updated apps. We tried this build on our machines and we can confirm that this build is stable enough for everyday usage. Gabe from Windows team today confirmed that this leaked build breaks flighting. So, Windows 10 Build 9901 will not receive future updates as part of Windows Insider program. But you will be able to upgrade it to future builds using ISOs. Gabe also tweeted that Microsoft is not concerned about leaked builds, but they would recommend users to try out officially released builds.
Read more about this leaked build and download link here.