Just this ^
Ever since yesterday, when clicking on some (quite unrelated!) threads, my iMac screen has been invaded by a great big swooping half page ad that either scrolls down or flies in from the side and blocks my screen until I close the ad graphic. Yesterday's ad featured a monkey. Today's ad is for Pizza Hut.
I'm on an iMac (the one with the great BIG screen so this invasion is all the larger!) using Chroma.