Earlier today, Microsoft released a security update KB4497165 for Windows 10 November 2019 and May 2019 feature updates. Because security updates are mandatory in Windows 10, it may have appeared on your Windows Update page or it may have been updated.
On the update log page, Microsoft said KB4497165 is primarily an update support for Intel microcodes. The security update was first introduced in January, but has now been re-launched by Microsoft, but has given no reason for the re-release.
On the Knowledge Base page, Microsoft notes that users should only install this particular update for selected Intel processors, but some users report that KB4497165 also appears on PCs that use AMD CPUs. Microsoft says Windows 10 microcode updates are installed like other updates, and Windows will automatically load updated microcodes through OS Loader to fix reported vulnerabilities.