Apple has released macOS Big Sur 11.5.2. The release notes mention only “bug fixes.” There are no security notes. What does it fix? We don’t know! Should you install it sooner or later? We have no idea! If you install it, let us know in the comments if you notice any difference at all.
Two things that aren’t mysterious: the macOS 11.5.1 Big Sur update weighs in at 2.54 GB for a 2020 27-inch iMac, and you can install it in System Preferences > Software Update.