I was getting errors accessing some sites (Google Drive for one) where I was being redirected to a support page telling me to update my browser. I use FF Dev as my default browser, and that’s like two steps away from bleeding edge, so I knew something was wrong.
Attached screenshot shows the “About Firefox Developer Edition” modal displaying the version number, over the console showing the results of navigator.userAgent as Firefox/65.0!
Sites should really be doing Feature Detection and not UA sniffing, but still!