Apple has released MacOS Big Sur 11.3.1 with fixes for two critical WebKit vulnerabilities.
Apple has also released security updates for Safari 14.1 on MacOS Catalina and MacOS Mojave that should be installed using the Mac App Store.
These vulnerabilities are being actively exploited in the wild. Users should update as soon as possible to avoid potential exploitation.
Important links for MacOS Big Sur users:
How to update MacOS
MacOS 11.3.1 Release Notes
Important links for MacOS Catalina and MacOS Mojave users:
How to update Safari
Safari 14.1 Release Notes