I believe this problem began in 133. I've noticed that if FF is open for a few hours, it starts to develop a very noticeable input lag. For example, if I'm watching a YouTube video and hit an arrow key to advance the video, there will be a couple of seconds before the browser registers the key press. It behaves like a high CPU issue but I do not detect high CPU usage when this is happening. Restarting the browser resolves the issue for a few hours.

This is happening on Windows 11 as well as on a Mac running Sonoma.