Sonoma/Sequoia: Fourth release candidate for security updates +++ iOS 26.5.1 is no longer signed | News

If a Mac is no longer supported by the latest macOS, it is not immediately discarded. Macs will continue to receive updates for at least two years. New features are generally not added; Instead, Apple plugs security gaps and ensures compatibility with the company’s own services (iCloud, Apple Music/TV/Arcade). Apple is currently putting together such a software package for macOS 15 Sequoia and macOS 14 Sonoma.

The updates are the fourth “release candidates” (RC 4). For both users registered as developers and participants in the beta program, a new beta version is available in the Settings app under /General/Software Update. As is now usual, Apple does not offer a direct download. Users who require beta install a software profile that handles authentication with Apple. The user can then choose between beta and stable branch in the software updates. Apple is keeping quiet about the content; The update probably includes similar security updates that were released for macOS 26 Tahoe last week. Over 25 vulnerabilities were eliminated, 17 of them in the in-house browser engine WebKit.

If a Mac is registered for beta testing, new versions are offered as downloadable updates.

No more signature for iOS 26.5.1
At Apple, installing system updates is now a complex process with many security checks. One of these is the verification of the system. The newly compiled system image is checked for correctness. The installation process draws on a security factor, the signature, live from Apple’s servers during the installation. Apple regularly provides signing for older versions and thus prevents them from being installed. This now affects iOS 26.5.1 after the update to 26.5.2 was released last week. Apple is expected to release iOS 26.6 next; the day before yesterday the fourth beta version was released.