Microsoft will be propagating Intel microcode updates to counteract the second variant of Spectre vulnerability to systems with the Windows 10 Fall Creators Update. Microsoft says it is now distributing those updates via the Microsoft Update Catalog.
Though Intel's release covered Kaby Lake, Coffee Lake, and Skylake platforms, Microsoft says its initial updates will only cover Skylake devices running the Windows 10 Fall Creators Update. The Skylake microcode update is listed as KB4090007. Microsoft says that more Intel microcode updates will be released as they're made available.
Aside from the new microcode updates, Microsoft warns that you'll want to make sure that your antivirus software is up to date in order to avoid any compatibility issues with further Windows updates. From Microsoft:
The continued focus of our work with our AV partners and customers is to manage the risk of compatibility issues, especially those that result from AV software that makes unsupported calls into Windows kernel memory. Due to this potential risk, we require that AV software is up to date and compatible. We will continue to require that an AV compatibility check is made before delivering the latest Windows security updates via Windows Update until we have a sufficient level of AV software compatibility. We recommend users check with their AV provider on compatibility of their installed AV software products.
So now Microsoft will archive both its own patches, and Intel's, too.
Currently, the microcode being archived is just a fraction of Intel's available patches (which so far cover the Skylake H-, S-, U-, and Y-series microprocessors). The microcode is available as part of a patch for Windows 10 version 1709 (the Fall Creators Update): KB4090007, which will be stored as part of Microsoft's Update Catalog. It's a standalone update, meaning it won't be part of a subsequent "rollup" update.
Microsoft warns that Windows Update will run a compatibility check with your antivirus suite before installing updates against Meltdown and Spectre. Earlier changes to the OS to resolve the vulnerabilities have led to problems with av-suites. Microsoft has worked with security software vendors to resolve them
