Apple issues Rapid Security Response update for iOS 16.4.1, macOS 13.3.1

A Rapid Security Response update is a special kind of update that doesn't require users to perform a normal software update. Instead of a lengthy update procedure, the update can instead be quickly downloaded and installed within minutes.

Tested in beta, the updates are intended to provide important security changes between the regular software updates. This can include fast fixes for urgent security issues, such as actively used exploits against Apple's software, with the RSR changes to mitigate risks of infection or data loss.

We've tested it across multiple devices. So far, as of 1:50 PM ET, every attempt to update has been met with a warning that the device cannot verify the security response. The warning goes on to say that the device is "no longer connected to the internet" when that isn't the case.

This may be a case of server load, but the download is very small. AppleInsider has reached out to Apple for comment.

RSRs are only to be delivered to the latest versions of iOS, iPadOS, and macOS, and do not apply to earlier releases.

When an RSR is applied, the update adds a letter to the end of the version number, for example turning iOS 16.4.1 to iOS 16.4.1 (a).

According to a new support document, the default setting is for the RSR to be applied automatically, and for users to be prompted to restart the device when required. RSR installation can be disabled, with the content of the RSR rolled into the next standard software update.

While the update is seemingly available to download straight away, you won't necessarily be able to install it. Tweets by @Dhinakg and @Aaronp613 reveal that the RSR has a "granular ramping logic," in that it will allow a percentage of users to install the update at a time.

If a screenshot of code is correct, only 5% of users will be able to install the update in the first 6 hours of release, rising to 15% by 12 hours, 40% by 24 hours after release, and 70% by hour 36. After 48 hours, all users who downloaded the update will be able to install it.

It is unclear how the proportion of users is selected.

Attempts to install the update before the device is allowed to will display a notice saying the iPhone is "Unable to Verify Security Response" and claiming it is because the device is "no longer connected to the internet." Despite the apparent lack of internet according to the message, users can still go online normally with their iPhone without restriction, and the notice only applies to the update.