The Windows 10 Creators Update, is supposed to happen around April 11th, on Patch Tuesday, as usual. But it appears that someone jumped the gun, and released the ISO images for the build, ahead of the official announcement.
The Verge reports that this new build is internally referred to as an RTM by Microsoft's team. That means this is the stable version of the Creators update.
RTM = Release to Manufacturing.
The URLs for the ISOs clearly mention the words Insider Preview. Speaking of which, Build 15063 was released to the Fast Ring in the Insider Preview channel, about 6 days ago. That means it could be buggy, though patches can always be added via updates.
You can view a list of the known bugs in Windows 10 Build 15063 at Microsoft's Blog.
Windows 10 does have a notorious history of bad updates, which we have seen personally, affecting the functionality of the OS slightly. (I experienced errors on shutdown about a year back, which was later fixed after an update).
These were the names of the ISOs which were leaked and later pulled from the Microsoft servers: Windows10_InsiderPreview_Client_x64_en-us_15063.iso and File name: Windows10_InsiderPreview_Client_x32_en-us_15063.iso
We have NOT tested this build on our PC and laptop, which are running on Windows 10 Build 14393.969 Anniversary Update. But, we advise readers something. If you managed to download the ISO before it was removed, please either wait for the official announcement before installing the update, or test it for bugs in a virtual machine.