URL: https://www.youtube.com/watch?v=

Browser / Version: Firefox 133.0
Operating System: Windows
Tested Another Browser: Yes Chrome

Problem type: Something else
Description: Cursor is visible on fullscreen Youtube videos
Steps to Reproduce:
Reproduce:

1. Open Youtube video with Firefox
2. Go to fullscreen
   => There should be a "blinking cursor" like on a command-line terminal on the left bottom part of the fullscreened-player. This "cursor" is a <'type here'> type of cursor, like if an element was highlighted by the user or there was a hidden input.

This is not the only place where the firefox "Cursor" goes wierd places. In the "about:addons" page, click on an installed addon (to view details) then select the "tree-dot button" like if you wanted to manage the addon. There, a blinking cursor will appear as well, like on the Youtube videos when fullscreened.

This issue is recent. I tried to pinpoint on Youtube which "div" was activated but without success, I can't see an html element with the inspector nor can I pinpoint which it would be in the html code, the only luck I got to move the blinking cursor up top by adding display:false; (css) to the html video container. The video was hidden and the cursor moved to the top of the fullscreen window. That's about it.

additional debug informations:

• It does not happened in Chrome. I have tried disabling any addons (failsafe mode) with Firefox and the issue is still present.
• I believe this is fairly recent? (so that would be 133.0.3 released on dec.10).
• I tried a portable Firefox version 133.0.0 (not the latest 133.0.3 minor version patch) and I do not have this bug, so it seems it's something linked to one of the latest patches (might help to pin down what)

View the screenshot

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