What Apple has done is what it normally does after an iOS release: it stopped signing the previous version. This means users running iOS 10.3.2 can no longer downgrade (eg to iOS 10.3.1) because the ‘sign off’ an upgrade looks for on Apple’s servers before installing will no longer be given.
Why is this a problem? Because of both iOS 10.3.2’s importance and its problems.
As explained in my upgrade guide, iOS 10.3.2 addresses multiple, serious security flaws. In fact Apple’s iOS 10.3.2 security page lists 23 categories of exploit with over 20 related to WebKit (aka Safari browsing) and two in iBooks which lead to the execution of arbitrary code that can take over your device.
So you should install iOS 10.3.2, but equally you may need to uninstall it promptly because the upgrade contains a serious battery problem which can kill iPhone battery life in well under an hour.
I exclusively reported this back in May and I’ve been contacted by numerous users and witnessed a lot of complaints across both social media and the official Apple Support Communities website (sources: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20... you get the picture).
Of course it is impossible to scientifically gauge the true global scale of the bug (I know iPhone 7 and iPhone 7 Plus users are unaffected), but putting more meat on the bones for me is reader Kamlesh Parmar, a technical support lead at a major enterprise services specialist.
He told me his affected iPhone 6 would even lose 10-20% within minutes of unplugging from a full charge and then switch off with up to 40% charge still remaining: “I've spoken to friends and they all report the same issue. I did a factory reset and then restored my iPhone, however I still have the issue.”
The only cure? Yes, you’re ahead of me: downgrade to iOS 10.3.1.
As such Apple’s decision to stop signing iOS 10.3.1 causes a lot of problems. Those wary of upgrading because of the battery issue will not now try the update and gain its critical security fixes because of the lack of an escape route if they are affected. While those already affected on iOS 10.3.2 can no longer downgrade and escape it - great.
But there is some good news: iOS 10.3.3 may not be far away.
Today Apple released iOS 10.3.3 beta six to both developers and the public. That’s an unusually high number of betas for a minor point release (some have no beta testing at all) and suggests Apple knows the importance of getting this update right. Surely one of the things on its hit list is addressing the battery problems of iOS 10.3.2.
As such, while I think Apple should not have stranded users on iOS 10.3.2 before the release of iOS 10.3.3, a solution may not be far away. And if your iPhone has been running out of battery within an hour or two since iOS 10.3.2 was released in May, that can’t come soon enough…