I discovered that I lost all the sessions from the OneTab extension that I have been using for a while. I am not sure when this happened, because I hadn't opened my OneTab in some time, but today I tried it because I wanted to file and categorize tabs I had saved, and they are sadly all gone! Searching around I discovered this probably has to do with recent Firefox updates, but I haven't been able to find any backup of my extension data. I followed directions from this issue https://support.mozilla.org/en-US/questions/1260116 and this https://www.tenforums.com/software-apps/176858-how-i-export-my-profile-data-firefox-extension.html. But no success. Any ideas if/where OneTab data could be? Or even which update could have broken the extension, if that could help? Thanks so much for any help :) Edit: I also wanted to add, because I saw it in some of the replies I found, that I have no Old Firefox Data folder, as I have never used the Refresh Firefox option. In fact, I remember getting a notification by Firefox some time ago to do this, but since it would involve having to reconfigure extensions etc, I chose not to (probably a bad idea!).