iOS 16.4.1 (a)

New Rapid Security Responses are delivered only for the latest version of iOS, iPadOS and macOS — beginning with iOS 16.4.1, iPadOS 16.4.1, and macOS 13.3.1.

By default, your device allows Rapid Security Responses to be applied automatically and, if necessary, will prompt you to restart your device. To check your device settings:

• iPhone or iPad: Go to Settings > General > Software Update > Automatic Updates, then make sure that "Security Responses & System Files" is turned on.
• Mac: Choose Apple menu  > System Settings. Click General in the sidebar, then click Software Update on the right. Click the Show Details button  next to Automatic Updates, then make sure that "Install Security Responses and system files" is turned on.

When a Rapid Security Response has been applied, a letter appears after the software version number, as in this example: macOS 13.3.1 (a).

If you choose to turn off this setting or not to apply Rapid Security Responses when they’re available, your device will receive relevant fixes or mitigations when they’re included in a subsequent software update.