Users on the second iOS 16.4 and macOS 13.3 betas have been given a new Rapid Security Response update as Apple tests the feature.
iOS 16.4 gets Rapid Security Response test update
Apple intends to use Rapid Security Response updates in the future to quickly address discovered security vulnerabilities that are being actively exploited. This is the first Rapid Security Response update for iOS 16.4 and macOS Ventura 13.3 beta testers.
The update can be found in the Settings app in the same place a normal update appears. This update is shown as iOS Security Response 16.4 (a) and macOS Security Response 13.3 (a).
Users that trigger the Security Response update are given the ability to revert to the previous iOS or macOS version during this test. Apple has tested this feature in previous betas.