Apple has sent Rapid Security Response updates to those testing the beta versions of macOS 13.3 and iOS 16.4.
The update can be found in the Settings app in the same place a normal update appears. It’s shown as iOS Security Response 16.4 (a) and macOS Security Response 13.3 (a).
Rapid Security Responses are designed to allow Apple to address security issues without requiring a full operating system update. that involve the operating system require the device to restart. Rapid Security Responses that involve Safari require the user to quit the app.
Apple says that Rapid Security Responses don’t adhere to the managed software update delay; however, because they apply only to the latest minor operating system version, if that minor operating system update is delayed, the response is also effectively delayed. If necessary, the user can also remove the responses.
