Apple has issued new firmware 4A400 for AirPods 2, AirPods Pro and AirPods Max. There are no release notes, as usual.
The firmware will be updated automatically in the background when the AirPods are charging and near a connected Apple device. When you see the popup shade, dismiss it with tapping on the X and leave the AirPods nearby.
It’s for the “Find My” feature for the Pro and Max AirPods
https://9to5mac.com/2021/10/05/apple-rolling-out-new-find-my-features-for-airpods-pro-and-airpods-max/