https://www.bleepingcomputer.com/news/microsoft/windows-10-kb5008212-and-kb5008206-updates-released/

December 2021 Patch Tuesday is rolling out to devices on Windows 10 version 2004, version 20H2, version 21H1 and version 21H2. As per the official release notes, Microsoft has published two cumulative updates - KB5008212 (newer versions) and KB5008206 (older versions).

Like the November release, this month's security updates include security fixes for November 2021 Update, May 2021 Update, October 2020 Update (version 20H2), and May 2020 Update (version 2004). It's also the last security update for version 2004, which has been retired today.