In my case I sometimes use the Ctrl+U and Ctrl+W keyboard shortcuts in Firefox by accident, since those are shortcuts to delete the line or word in the Linux terminal (and works in a lot of other Linux apps too), and while accidentally opening the so...
On Linux Ctrl+W is a shortcut to delete the word just behind the cursor (like Ctrl+Backspace) which works on the terminal as well as most other native Linux apps, however Firefox also uses that for closing the current tab. Now if Firefox was using th...