Unexpected update to Nik Collection 5.9--but what was updated?

I am still using Nik Collection 5. The latest version was 5.8. A few days ago, the program notified me of an (unexpected) update to 5.9 (which did not include release notes).

Can anyone point me to release notes or some other info about what was updated?

Go here and select “Previous versions”

https://support.dxo.com/hc/en-us/categories/115002389907