Not a straight block, but a super handy extension is BehindTheOverlay. It gives you a consistently placed button that removes overlays. Instead of hunting for an X or cancel or close button, you use your muscle memory and always hit the same place in the Chrome.

https://chrome.google.com/webstore/detail/behindtheoverlay/l...

https://addons.mozilla.org/en-US/firefox/addon/behind_the_ov...

https://github.com/NicolaeNMV/BehindTheOverlay