What article on docs.github.com is affected?
Lost so much work due to this, open file in repository, edit it in web, press back arrow in Firefox, Firefox asks "This page is asking you to confirm that you want to leave — information you’ve entered may not be saved.", I press "Stay on Page", options were that or "Leave Page", GitHub then asks "You have unsaved changes. Do you want to discard them?", I say "Cancel", options were that or "OK" but the page leaves anyway, losing entered work. No options can prevent loss in this case. GitHub shouldn't ask to leave the page if Firefox prevents it. There is an issue here.
What part(s) of the article would you like to see updated?
Warn of this issue or fix it.