Hot on the heels of the iOS 10.3 update (see “iOS 10.3 Adds New File System, Find My AirPods, and More,” 27 March 2017), Apple has rolled out iOS 10.3.1 with a bare minimum of release notes: “iOS 10.3.1 includes bug fixes and improves the security of your iPhone or iPad.” You can install the roughly 30 MB update via Settings > General > Software Update or through iTunes.
Apple lists only one security fix, but it’s a doozy, and undoubtedly explains why Apple pushed 10.3.1 out so quickly. The update addresses an exploit that could have enabled an attacker within range to execute arbitrary code on the Wi-Fi chip in an iOS device. We hope this bug existed only in iOS 10.3.
If you have already updated to iOS 10.3, we recommend installing 10.3.1 to get this security fix. If you’re still running iOS 10.2.1, stick with it for another week or so to make sure 10.3.1 doesn’t introduce some new problem.