Apple’s Hidden iPhone Update Recommended For Hundreds Of Millions Of Users
This post, originally published on Wednesday, March 18, was updated on Thursday, March 19 to include more information about the first Background Security Improvement update.
Apple has released the first Background Security Improvement update for iPhone, called iOS 26.3.1(a), along with corresponding updates for iPad and Mac. This aims to fix a security vulnerability on the iPhone, but it appears differently on the iPhone than the standard software versions. Here’s how to find and install it — and it’s not where you expect to find it.
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The Evolution of the ‘Silent’ Security Patch
Three years ago, Apple had a different process for emergency security-focused updates, called Rapid Security Responses. These have been deprecated, and earlier this year Apple implemented the framework for BSI updates instead.
Which iPhones Can Run iOS 26.3.1 (a)?
Even though it is a new version, it is for all iPhones starting from iPhone 11, i.e. all iPhones released from 2019 to date. Second-generation and third-generation iPhone SE mobile phones are included. All members of the iPhone 17 series and iPhone Air are also supported.
Apple’s notes say that this BSI “provides additional protection and is recommended for all users”; That means hundreds of millions of iPhones compatible with iOS 26. “Background Security Enhancements deliver significant security improvements between software updates,” the company said. a support document.
How to Download and Install iOS 26.3.1 (a)
Most importantly, this update isn’t in the same place where you’ll find regular updates. Open the Settings app on iPhone and scroll down to Privacy & Security. At the bottom right you will see Background Security Improvements. Click on that, there is an option to Install Automatically. But that’s not always the fastest way to get there. If a new BSI is available you can choose to download it. On my iPhone 17 Pro Max. Downloaded and installed quickly; in less than 5 minutes in total.
Note that unlike regular updates, you can uninstall it once it’s installed. To do this, click on the “i” to the right of BSI; The option to remove it and restart the phone appears.
iOS 26.3 .1 (a) — What’s in the Release?
On the support page mentioned above, Apple said that this BSI was designed to fix an issue in WebKit, the open-source browser engine that displays web content in apps.
The issue, tracked as CVE-2026-20643, is a “cross-origin” bug in the Navigation API. It deals with maliciously crafted web content that allows an attacker to bypass the Same Origin Policy and potentially access sensitive data in other open tabs. In this update, this issue has been fixed with what Apple calls “enhanced login verification.” Since WebKit powers Safari and in-app browsers, this is considered an immediate solution for all users.
