Windows brightness changed after launching 'Unreal Level Editor' and doesn't go back to normal

I downloaded Killing Floor SDK to my PC and started it, immediately found out that my brightness went up (not only inside of the app but outside too, browser pages etc etc were affected). When I closed it it didn’t go back to normal. I tried to change it manually but I can’t find the setting because it’s gone, all the screenshots I found have it and I don’t. Right now I’ve downloaded it once more and brightness went up even further but at least now when I close it it goes back to where it was before I launched it (still higher than I had before launching it the first time though). Please send help, my eyes are melting.