Microsoft released two new Windows updates meant to fix the Spectre v2 vulnerability. KB4078407 and KB4091666 are for Intel users only. Microsoft tried to release these updates on January 4, a day after news of the flaws became public. The first set of patches released back then caused some systems to experience higher reboot rates or boot-up issues. Microsoft eventually paused the rollout of some of the Spectre patches. The other two are Meltdown and Spectre v1, which are known to affect almost all CPUs released in the past 20 to 25 years.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-releases-two-new-windows-updates-containing-new-spectre-2-mitigations/