Apple will let you remove security patches installed by iOS 16’s Rapid Security Response system, which can install patches without having to fully update your iPhone (or even restart it, in some cases). According to a supporting document identified by MacRumors, you can remove a Rapid Security Response update by going to Settings > General > About, then tapping the iOS version. From there, a “Remove Security Update” button will appear.
The document doesn’t give any examples of why you’d need to uninstall any of the patches, leaving your phone open to the vulnerability it protects against. It’s easy to imagine a few special circumstances where the feature could come in handy, perhaps messing up some special work-related software or management tools, for example. Otherwise it’s one of those features that most people probably should never use unless they have a very specific reason and they fully understand what they’re doing – kind of like the new extreme lockdown mode, which is included to protect users against “very sophisticated” targeted cyberattacks.
Rapid Security Response is enabled by default, although you can disable updates by going to Settings > General > Software update > Automatic updates and toggling “Security responses and system files”. If you do, you’ll have to wait for full iOS updates to get security patches. Again, I personally advise against disabling the feature unless you have an explicit reason to, given the number of recent updates from Apple that have fixed some pretty serious vulnerabilities.
The system is also coming to macOS in Ventura, which has yet to be officially released. So far, Apple’s support documents for its desktop operating system don’t mention whether you’ll be able to roll back those updates as well.