Apple released the iOS 11.3.1 update for iPhones on Tuesday, April 24, 26 days after the official release of iOS 11.3 and eight days after the iOS 11.4 beta 2 update. It is the first minor update to iOS 11.3, and the biggest thing in it is a fix that lets displays fixed by third parties work again.
Users running an iPhone 5S or newer can download the update right now. Go to "General" in your Settings app, then hit "Software Update." Follow the on-screen instructions when the update appears to download and install iOS 11.3.1.
Overall, iOS 11.3.1 appears to mostly fix bugs and implement security patches. The big thing, as mentioned briefly above, is that it does include a fix for issues stemming from third-party display repairs. iPhone 8 users running iOS 11.3 would, unfortunately, find their displays bricked after a repair from a third-party vendor — even if they used an official display. So as long as you have iOS 11.3.1 or later, there should be no more issues with your repaired display.
Something not fixed is the broken 3D Touch issue. Whenever you first unlock your iPhone, 3D Touch doesn't always work right away. If you try it on a home screen app, you might go into edit mode instead of seeing the 3D Touch options. Apple still has not fixed this, so we're hoping for an iOS 11.3.2 coming soon for it, though that's a longshot. There's also the buggy screenshot issue that appeared in iOS 11.3, though we haven't yet confirmed whether it's been fixed or not in iOS 11.3.1.
Aside from those things, iOS 11.3.1 also addresses a few security issues. An issue where an application could gain elevated privileges with Crash Reporter was patched. LinkPresentation was fixed, preventing the spoofing of URLs in QR codes scanned with the Camera app and elsewhere. Apple also fixed two issues where "processing maliciously crafted web content may lead to arbitrary code execution."
We haven't uncovered much else of importance in iOS 11.3.1, but if we find something, we'll be sure to update this article with the details.
iOS 11.3 as a whole brought new features to iPhones. iPhone X users received new animoji, while all iPhones got Health Records in the Health app, Business Chat, and, most notably, battery health tools and power throttling options. These last two options were pushed after news that Apple would secretly slow down iPhones with aging batteries.
While iOS 11.3.1 is now the most up-to-date version of iOS, it's still missing some crucial features promised for iOS 11. Messages on iCloud, teased during the iOS 11.3 beta, is gone, as is AirPlay 2. We're hoping these major features make their way to 11.4, but given iOS 11's track record with bugs, we're willing to wait for functioning versions.