Microsoft is no stranger to software incidents and leaks, but this one sounds pretty serious. Apparently, the Redmond firm accidentally leaked an in-development build for insiders, on both PC and mobile.

Those who installed a fresh build on Thursday evening actually got the internal build of Windows 10 (16212), which is still a work in progress. Microsoft caught the error on time and only a small number of people could download the update. Those who managed to get hold of the mobile build were left with a bricked device, which is quite serious.

Microsoft’s team says that an “inadvertent deployment to the engineering system that controls the builds” happened. Sadly even some retail devices that aren’t part of the Insider program got the the update and may have been bricked. People are talking about unending reboot loops and the solution is to use the Microsoft Windows Device Recovery Tool to wipe and restore the machine.

That’s all mobile, as the PC build has no known critical issues for now. Users can wait until a new build comes, or just use the Windows 10 recovery option and revert to the older build. And in fresher news, it appears that the future version will bring the Windows Phone keyboard WordFlow to PCs and tablets. File History is also ready to be gone from the desktop.