When I hit "edit" and then "back" - it goes back without asking.
But when I hit "edit", click with the mouse on the text, and then hit "back", it asks: "This page is asking you to confirm that you want to leave - data you have entered may not be saved.", as if I changed something.
It falsely detects the change when there is no change.
See also: (April 2015) T95150: CodeMirror should not ask confirmation when user leaves page that has no changes