I have just spent a long time looking for PDFs I really need and when I closed Firefox it deleted every single PDF in my downloads folder (including ones that weren't downloaded during this session) The PDFs weren't just opened as a website in Firefox, I've downloaded all of them as permanent files and just opened them in Firefox to confirm they work. I have set my browser to automatically delete download history so I can't redownload them that way (and I would prefer to keep this setting on), however I have never set Firefox to automatically delete any kind of downloaded file (I don't know if this is even available in settings). I have also checked my antivirus quarantine just in case, but it is empty so I doubt anything was deleted due to possibility of malware. Is there any way to prevent Firefox from doing this and is there any way I could restore the files. At this point, I can't even begin to remember everything that I may have lost due to this bug and searching and downloading everything manually again may take me days.