Apple released iOS 15.1.1 for the iPhone 12 & 13 lineups a couple of Mondays ago with an important bug fix pertaining to dropped phone calls. Although I hadn’t experienced this problem myself, it was obviously experienced by enough users that it warranted a resolution from the OEM.
Of course, Apple’s software updates are always a double-edged sword because it doesn’t take long after an update gets released for the company to stop signing the previous version of iOS or iPadOS. In this case, that means Apple is no longer signing iOS 15.1 for the iPhone 12 & 13 lineups (Apple continues to sign iOS & iPadOS 15.1 for all other devices).
When Apple stops signing a firmware, this makes it more difficult for the end user of an iPhone or iPad to downgrade to that particular version. This is because Apple configures its firmware servers to deny restore requests to that version of iOS or iPadOS and instead prompt the user to download and install the latest version.
While the downgrade would still possible if the user has the correct resources, including saved .shsh2 blobs and access to third-party software, anyone else who tries downgrading to an unsigned firmware using the traditional method will be met with an error message in Finder or iTunes – whichever they’re using.
Software downgrades are more popular among jailbreakers than the general populace because they permit users to revert to firmware that may still be susceptible to the exploits harnessed by jailbreak tools. Downgrades may also be used by non-jailbreakers to revert to an older firmware after a software update destabilizes a particular device by introducing new bugs.
In this case, there are no public jailbreaks for any version of iOS or iPadOS 15, so this isn’t that big of a deal for jailbreakers.
While I’d personally like to see Apple granting users the ability to install any firmware they want on their devices, that’s unlikely to happen anytime soon. Apple executives made it appallingly clear when discussing sideloading apps that they prefer controlling their user base and deciding what’s best for them. The motive seems no different here as Apple claims that the company feels responsible for user security.
If you’re ever interested in learning what version(s) of iOS or iPadOS are being signed for your iPhone or iPad, then you can visit the handy online IPSW.me website to find out. You can also use our downloads page to get any firmware file you might require for your restore or downgrade.