Apple has released MacOS Big Sur 11.3 with fixes for at least 59 security issues. There is also an important update for Xcode 12.5 that should be installed using the Mac App Store.
Apple has also released security updates for MacOS Catalina and MacOS Mojave. There is also an important update for Safari 14.1 that should be installed using the Mac App Store.
Users should update as soon as possible to avoid potential exploitation.
Important links for MacOS Catalina and MacOS Mojave users:
How to update MacOS
Security Update 2021-002 Catalina Release Notes
Security Update 2021-003 Mojave Release Notes
How to update Safari
Safari 14.1 Release Notes