Sorry for your problem with a 3rd party add-on for Firefox. Do you realize the shear number of add-ons available for Firefox? Tens of thousands that Mozilla would have to 'test' to ensure compatibility. Not their responsibility, but rather the responsibility of the developers who create add-ons to work with Firefox. There are mailing lists that add-on developers can sign up for with Mozilla to keep them informed of the upcoming changes to Firefox and how those changes might affect their add-on. -------------- That said, this may 'fix' your problem for Firefox 43, but won't work in later versions. That extension has to be fixed by its' developer in the long run to ensure it keeps working in the future. 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 44 (Release slated for Jan 26. 2016) 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. Otherwise the users of those extensions will be SOL come the release of Firefox 44. ''Mozilla has already pushed back the version in which this new security feature was to be enabled from Firefox 40 to 44. I doubt if there will be any further reprieve.''