Apple on Monday made the surprise release of iOS 10.3.1, available for iPhones, iPads, and iPod touches as an over-the-air update or when connected to iTunes via a Mac or Windows PC. [Updated with release notes]
In an unusual twist for Apple, no release notes are available. The update is also small, potentially under 30 megabytes as an OTA download.
The release appears related to problems with iOS 10.3, launched a week ago. Shortly thereafter Apple killed the OTA update for the iPhone 5 and 5c, suggesting a hardware-specific problem. AppleInsider can confirm that those downloads have been restored.
The 5 and 5c were Apple's last iPhone models with a 32-bit processor, the A6. Since the iPhone 5s all iOS devices have turned to 64-bit technology. Apple is in the process of phasing out 32-bit support, and indeed the iOS 10.3.2 beta appears to omit it entirely.
One of the core changes in iOS 10.3 was the switch to the Apple File System, better optimized for flash storage. In some cases it restored gigabytes of storage space.
Update: Release notes are now available, and point to bugfixes and security updates. In the latter category Apple has solved a vulnerability that would let hackers run attacks through a device's Wi-Fi chip.