Apple released macOS 11.3 on April 26, 2021 to the public. The 11.3 update to Big Sur is available to all compatible systems.
This update includes a serious security update that fixes a zero-day exploit related to the File Quarantine and GateKeeper system in macOS. The security update is backwards compatible with macOS Catalina and macOS Mojave for users still on those OSes. Apple was aware of an attack on this system that could lead to someone downloading and running malicious software that was able to get around these protections Apple has in place. This particular flaw was already being used in an attack vector against macOS users on the internet and through various software download and Mac-related websites.
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Beyond the security updates, macOS 11.3 has changes for M1 Macs, including the ability for iPhone and iPad apps running on M1 Macs to be resized.
The macOS 11.3 update also adds features available to users in iOS 14.5, which was released the same day. These features include the ability to use AirTags in the Find My app, new emoji and new Siri voices.
For those who game on their macOS devices, Apple added support for Xbox Series X/S and PlayStation 5 controllers, complete with haptic/vibration support. In addition, iPhone and iPad games running on the M1 Macs gained keyboard, mouse and trackpad support for games that were already compatible with controllers.
This macOS 11.3 update is advised for all users to upgrade immediately due to the security patches included.