Apple has released the first public Background Security Improvement for iPhone, iPad, and Mac. There are four versions of the release.

These are the four versions available today:

• iOS 26.3.1 (a)
• iPadOS 26.3.1 (a)
• macOS 26.3.1 (a)
• macOS 26.3.2 (a)

The reason for two macOS releases is likely due to Apple’s new MacBook Neo having a newer version of macOS 26 than all other Macs running macOS Tahoe.

Apple describes today’s Background Security Improvement as a patch for WebKit:

Impact: Processing maliciously crafted web content may bypass Same Origin Policy

Description: A cross-origin issue in the Navigation API was addressed with improved input validation.

Before today’s first public release, Apple released multiple sample Background Security Improvement updates to test the system.

Apple says the system can “deliver lightweight security releases for components such as the Safari browser, WebKit framework stack, and other system libraries that benefit from smaller, ongoing security patches between software updates.”

Here’s how to check for the latest Background Security Improvement release manually:

• On iPhone and iPad: Go to Settings, then tap Privacy & Security.
• On Mac: From Apple menu , choose System Settings. Then click Privacy & Security.