When I put firefox in fullscreen mode, either by maximizing the window in sway (a wayland window manager), pressing f11, or fullscreening a video, colorful glitched pixels appear wherever there's motion on the screen. For example when scrolling, these glitches appear around the edges of things, or when watching a video, the glitches appear around things moving in the video. I can't demonstrate, because the problem goes away when I try to record the screen. Safe mode doesn't help. The problem is not present under X11, or when using chromium instead. It's been like this for a few months.