Apple has released the macOS 11.6.4 update to macOS Big Sur, containing security fixes along with macOS Catalina Security Update. The recent update is available on all Macs using the Software Update section of System Preferences.
The latest update has released after the last Big Sur update of 11.6.3.

Furthermore, the new release macOS Big Sur 11.6.4 “improves the security of macOS” and is recommended for all users. Additionally, Apple has also released a 2022-002 macOS Catalina security update for those still running macOS Catalina.