Microsoft has released also a Microcode update KB4100347 for Windows 10 April Update to mitigate the Spectre V2 vulnerability.
Microsoft has provided a number of Intel Microcode updates for various Windows 10 versions (see link list at the end of the article). Unlike microcode updates, which are rolled out by the board manufacturers for the BIOS or UEFI, Windows loads the new microcode on system startup.
After installing Windows 10 April Update (V1803), users quickly noticed that the Spectre V2 microcode was not included (see Windows 10 April Update: Bugs and Issues). For Patchday (May 8, 2018), only special microcode updates for AMD CPUs for Windows 10 version 1607 were rolled out (see Windows 10 security updates May 8, 2018).
Update KB4100347, released on May 15, 2018, is the microcode update to mitigate the Specte V2 vulnerability (CVE 2017-5715 [“Branch Target Injection”]). It is available for Windows Server version 1803 and for Windows 10 version 1803 clients. Please note, however, that the update only applies to certain CPUs listed in article KB4100347. If required, the update can also be downloaded via Microsoft Update Catalog.
Windows 10 April Update available (April 30, 2018)
Windows 10 April Update (Version 1803): Upgrade FAQ
Windows 10 Fall April Update – Upgrade Tips
Windows 10 April Update: Bugs and Issues
Windows 10: Microcode updates KB4090007, KB4091663, KB4091664, KB4091666, KB4078407