I am using Firefox 127 on Ubuntu. When I press the Control key, I often lose focus in the window I am currently viewing. This is annoying as it prevents me from copy-pasting for example. Sometimes the focus is back when I release Control, sometimes it is lost and I have to click again on the text field. It does not happen on all websites, for example support.mozilla.org works well, but it happens on duckduckgo or overleaf. It does not seem to be the same as existing issues such as [[https://support.mozilla.org/en-US/questions/1191486#search the "show mouse when press Ctrl" of Ubuntu]] (it is disabled) or [https://superuser.com/questions/1090673/why-does-the-active-firefox-window-occasionally-lose-focus an addon] (the problem still happens in safe mode). In case it is useful, when I press Control the tab bar background goes slightly darker, see attached images. Thanks for your help :) Nicolas