I turned the PC off this morning as I was going away. It started the MS updating thing and I let it do it and then rebooted to finish the job. I start it up tonight and my last version of legacy Ff is gone. How could that happen? The last legacy version of Theme Font & Size changer still had auto update (which renders the look) turned off. The craziest thing is my Reflect images of two days ago render the new Firefox! All of this seems impossible!
if you have enabled firefox updates then you got nuts. if you have not installed 52esr then you got also nuts. but please dont expect a full system analysis - YOU know best what you had set up and installed. maybe you have an updater software running, or some questionable antivirus is working. who knows if not you!?
You can install the old version back again anytime. Even the very first version of Firefox is possible, if you like it (only it will not work on current Windows versions). What's the question. Do not know where to get the installer? Tell me, I'll give you a link, all are official Firefox server links.
ESR https://www.mozilla.org/en-US/firefox/organizations/all/ current https://www.mozilla.org/en-US/firefox/all/ using any other is not responsible, in special when speaking about latest -> meltdown/spectre. the next issue for him may that that a newer quantum build than esr could messed up his profile. quantum (v57++) is not compatible to <=v56. create a new profile http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows or http://kb.mozillazine.org/Profile_Manager This article explains how to selectively transfer Firefox user data and settings to a new Firefox profile http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox
I have had to install the old version, turn off auto updates and get the global font tool installed separately. Now everything is back the way it was before with FF and I hate, hate, hate tiny fonts! Hard on the eyes and made FF for me unusable.
