Wow, this is awful. Some people reported that these ads are also very petty and not necessarily related to the game, like apparently Elden Ring shows an ad for a licensed mousepad when you hover over the game now…
Edit: Playstation Product Manager says this is actually a new bug. I really doubt it but they do seem to be “fixing it”.
For those already owning one - try setting up pihole or an equivalent. Sony could be serving ads from a domain used by something like a cdn, but I bet they don’t.
It’s not an ad per se. They’re replacing the key art and game logo with the picture and title of the latest news post for the game you’re on.