When switching to full-screen mode in Firefox while watching a video, the cursor won't disappear automatically until you move it. This issue affects all players except the native Firefox player. The bug appeared in version 143 and higher (affects all builds, including stable, Beta, and Nightly). I've tested the issue by rolling back the browser to versions 140 and 142.0.1, and everything works fine. There's a thread about this issue on the Bugzilla forum. macOS versions Tahoe 26.0 and Sequoia 15.7 are currently running. I can't test on other systems.