When I click the mouse wheel, anywhere on Firefox, the screen momentarily shrinks. The window looks the same as full screen, but shrunk to about a quarter normal size and centered on what looks like a tab group square. My desktop wallpaper shows behind this square, but no icons show. When I click on the window it returns to full size. This is incredibly annoying. I want to be able to use my middle-click instead of constantly right-clicking and then choosing from the menu. I disabled addons and restarted but got the same result so I assume this is something new in Firefox itself.