There appears to be something completely broken in the latest Firefox UI for me. Its making me want to throw my laptop out the window. When I have text selected in fields such as the address bar, or fields, sometimes rather than 'overwriting' the selection, it appends it. Or sometimes when I select all the text in a field and paste, I end up with the original selection appended by the pasted text, or vice-versa. It makes interacting with websites via the keyboard absolutely pointless in this browser. Main affected site for me has been the amazon web services console, which is my main use-case for Firefox due to containers, however apparently Chrome now has a parallel function for that, so I'll spend the rest of the night looking that one up, since Chrome is not exhibiting this issue.