Microsoft has released a security update for the Spectre v2 (branch target injection) vulnerability. Unlike KB4091666, published earlier in the week, which updated the Intel microcode to mitigate Spectre V2 at the chip level, KB4078407 is a software based fix for Windows 10 and Windows Server 2016 the two updates together should fully mitigate against Spectre V2. KB4079407 is a re-issue of the aborted fixes released in early January which caused issues on some systems.
Article Link: https://isc.sans.edu/diary/rss/23601