After hours and hours of surfing and worry, I never found an actual full explanation as to what is involved in using the Unbranded Firefox (to allow unsigned plugins - with warning, to continue to function), which is actually "Nightly" branded. So, I finally got it going, and am providing this information... Enjoy! Ok, we finally have some info that I had to pick around at huge time waste and get working for me, looks like... Here is what I have found/done. Let me know if any is wrong... If you want a Firefox that honors the about:config setting xpinstall.signatures.required with false, and allows unsigned plugins, then go to https://wiki.mozilla.org/Add-ons/Extension_Signing#Unbranded_Builds and install from the Latest Release Builds section to get the UNBRANDED (Nightly branding). I used the Windows 32-bit installer link. Note the name in that link (it has the release nubers in it), and download/save from the link, so you can tell next time when you try it again, and if it says duplicate, you know the link is not updated yet, and you will have saved your previous download for future backout, etc. I do see that the page/link was updated later in the day on 09/20/16 when 49 came out, so it looks to be being updated. :-) I did this the day before 49 came out, and got 48.0.2, just as I wanted. I Installed over 47.0.1 (or .2, I forget, but whatever). All of my settings and config info was retained, as far as I can tell, I did have a cloud.7 norton insight quarantine a dll file that stopped nightly from starting - after I later rebooted - and I restored it. Nightly is installed in a different program folder, so I was able to use 47.0.1 when 48.0.2 would not start, to google the problem, etc. Norton might not like that location, and name nightly for a browser, is all I could figure out, so I restoted/excluded that dll file. When I then clicked on the download and installed, it installed as Mozilla Developer Preview, but the browser is named Nightly, by the way. Everything looked good, except Nightly is a dark blue ball, and desktop icons that had firefox or ie as browser shortcut, all turned dary, but hey - ok! Today, I got a notice that Firefox 49 is available, so Nightly does let us know when an update is available, and it also showed up in Help/About, but I didn't fall for it. The page I mentioned above was not updated yet, but now it is. So looks like we have notification (be sure to turn off auto update, but notify works - my options carried over), but need to wait until the page/link is updated (and maybe a few days), and download/save from there. In fact, the download is over 40 meg so it is the full install (? I guess), so doing the updates this way looks to keep a trail and fallback that I didn't previously have, so this could be an improvement - wow!