Starting with Firefox version 48, the add-on signing requirement will be enforced with no override in Release and Beta versions of Firefox. See the MozillaWiki article; https://wiki.mozilla.org/Add-ons/Extension_Signing for more information. This will disable add-on signature enforcement; Firefox ESR version only. Enter '''about:config''' into your Firefox address bar Click the '''I'll be careful''' button Find '''xpinstall.signatures.required''' in the list Right click the preference Select Toggle until the value is false https://support.mozilla.org/en-US/kb/add-on-signing-in-firefox You can install the Firefox ESR 52 version which will get security updates into early 2018, to get "more time" using Firefox. [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]