There’s no change in the T2 firmware, nor in the iBoot version number of M1 Macs. There don’t appear to be any firmware updates, except possibly for some Intel Macs which lack a T2 chip. For those running a local Content Caching Server, M1 Macs still need to download the first 910 MB of this update direct from Apple’s servers, so there has been no improvement in this update in terms of efficiency. Intel Macs get a little over 2.5 GB, and M1 Macs 3.45 GB, suggesting it has an effective payload of about 300 MB of “bug fixes”. This is more than a minimal update, such as 11.5.1 which fixed a single vulnerability. Apple has left us completely in the dark, except …
The surprise update to Big Sur, bringing it to version 11.5.2, is the first that I can recall that has absolutely no release notes at all: none for users, who are merely told that it “includes bug fixes”, none for system administrators, and no security release notes.
