The first batch of security updates or ‘B’ updates for the month of ‘December 2020’ is now available for all supported versions of Windows 10 including version 20H2. If you want to grab these updates, check for updates in the Settings and the update will begin installing. The cumulative update comes with security fixes and general bug fixes, and the patch is rolling out to PCs with October 2020 Update, May 2020 Update , November 2019 Update, and later (depending on the edition of Windows installed)
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-cumulative-updates-kb4592449-and-kb4592438-released/