There is an override that you can enable to allow unsigned add-ons to be enabled. https://support.mozilla.org/en-US/kb/add-on-signing-in-firefox#w_what-can-i-do-if-firefox-disables-an-installed-unsigned-add-on '''Override add-on signing (advanced users):''' You can override this setting by changing the '''xpinstall.signatures.required''' preference to '''''false''''' in the [https://support.mozilla.org/en-US/kb/about-config-editor-firefox Firefox Configuration Editor] (about:config typed in the URL bar). Support is not available for any changes made with the Configuration Editor so please do this at your own risk. Note: That pref will be gone in Firefox 47, a few months down the road. So user's of currently un-signed extensions should contact the developers of those extensions and prod them into getting their act together & get their extensions signed by Mozilla.