There is but you will have to take the risk of security holes in older Browser when going on the internet. Others here can give you links but aren't responsibility if something happens should you use a older Browser.

I understand that but we are only using mozilla firefox to perform one task which is on our local network.. What is the option to completely disable updates.

First, Type '''about:preferences#advanced'''<enter> in the address bar. Under '''Advanced, ''' Select '''Update. ''' [v56+] Type '''about:preferences#general'''<enter> in the address bar. Select '''Update. ''' Select '''Never Check For Updates.''' Also turn off '''Use a background service to install updates''' --------------- [https://support.mozilla.org/en-US/kb/install-older-version-of-firefox?cache=no Install Older Version Of Firefox] {web link} Be sure to read everything here. If you still want to downgrade, look under; '''I still want to downgrade. ''' Click the '''Directory of other versions and languages''' link. Look for the directory of the version that you want. But, remember that '''old versions may have security issues. ''' You should also check out [https://www.mozilla.org/en-US/firefox/organizations/ Firefox; Extended Support Release] {web link} [https://www.mozilla.org/en-US/firefox/organizations/notes/ ESR Notes] [https://www.mozilla.org/en-US/firefox/organizations/system-requirements/ System Requirements]