Although it brings a record number of 143 security fixes, changes in version 26.6 seem fairly modest in size and scope.

A full list of all the vulnerabilities addressed is given in Apple’s security release notes. Other than those, the only explicit information about changes is the cryptic note that this “optimizes the Spotlight index in preparation for macOS 27”.

The build number for 26.6 is 25G72. Apple silicon Macs have a firmware update bringing them to mBoot 18000.161.9. This update is also provided in the security updates to Sequoia and Sonoma, syncing their firmware at last.

In bundled apps, there are plenty of routine or small build increments, but no evidence of more substantial changes. Safari is updated to version 26.6 (21624.4.5.11.5).

There are abundant increments in build numbers reflecting routine maintenance, but few more substantial changes apparent in /System/Library, including:

• Archive Utility has a build increment
• In kernel extensions, all AGX components are updated, as is AppleJPEGDriver
• There are six new AppleT8150 kernel extensions, suggesting support for forthcoming hardware
• There’s a new kext IOKitCrashQuiz1
• APFS is incremented to version 2811.160.7
• Many public and private frameworks are updated
• There’s a new private framework MapsBlastDoorSupport, presumably relating to a vulnerability that allowed malicious code to break out of its sandbox
• Spotlight RichText.mdimporter hasn’t been updated, though.

Patrick Wardle has also drawn attention to a change in the leaf certificate used to sign Apple binaries to “macOS Software Signing”, where previously it was just “Software Signing”.