Microsoft last pushed Windows 10 Build 10586.318 as May cumulative update to all the PCs running Windows 10 Version 1511 (Build 10586.xxx) and you can read the full official changelog by clicking here. Now the Build 10586.318 is available on Microsoft’s production servers and can be downloaded as CAB files of Cumulative update KB3156421 using the official Microsoft update catalogue links.
Click on the below official links to download it for both X64 and X86 devices in case you need them for updating your system.
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