https://www.pcgamer.com/microsoft-is-distributing-a-new-microcode-fix-for-spectre-vulnerability/

Microsoft is now releasing Intel’s newly approved firmware updates through the Windows Update Catalog. The new patch, marked KB4090007, adds firmware coverage to Intel’s Skylake H/S/U/Y and U23e series processors running Windows 10 version 1709 (Fall’s Creator’s Update).

The new patch includes Intel’s latest microcode release for Spectre Variant 2 CVE-2017-5715 “Branch Target Injection” vulnerability. In a nutshell, branch target injection wipes the intended memory address of a indirect branch, forcing the CPU to retrieve the true address which takes a few hundred cycles. During this time, the CPU will speculatively execute instructions based on branch prediction.