Just found a horrible bug on the Kindle app after the upgrade. I went to read my book and when it open the brightness suddenly went to 50%!
The System brightness slider was still all the way down. I was blinded as I'm in a dark room.
Luckily Screen Dim does work so I turned it on and it override the bug. I was able to read. Just remember to close the book before turning it off unless you want to see spots.
I reported it to Kindle Support.