Here's a screen shot from Firefox 92.0.1 for comparison before I go back to 93.0 (and try to figure out if I can recover all the bookmarks that I lost by downgrading). Note the game is more transparent in 93.0 (you can easily see the background image).
The problem is definitely with the latest Firefox 93.0. I downgraded to 92.0.1 and everything looks normal again. This isn't a solution as it's important to stay current with security updates.
Here's another screen shot that illustrates my issue. Note how the small in-game text is hard to see, yet the text outside the game window perimeter is perfectly clear.
I'm not saying it's impossible that it's something on my end (like graphics driver (which I haven't changed recently)), just not likely. It's only affecting Candy Crush - nothing else. I tested MS Edge and it has the same issue. Definitely not my internet speed: Download = 487 Mbps, Upload = 11.94 Mbps What browser and OS…