I believe I have seen this issue with Firefox also. I assumed it was because Firefox uses XWayland.
** Changed in: gnome-shell (Ubuntu) Status: Incomplete => New -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gnome-shell in Ubuntu. https://bugs.launchpad.net/bugs/1706476 Title: "julyshakedown" mysterious shadow around window when check marking and option box inside of window. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1706476/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs