[FIX] Armageddon in Firefox: Most add-ons disabled!

On 4 May 2019, 6:00 AM PST, one of the Firefox digital certificates used to sign add-ons expired. With this certificate no longer able to verify the authenticity of the add-ons, user across the faced the loss of access to their Firefox add-ons. This post teaches you how to recover from this failure in about 15 minutes and resume your daily routine work as if this has never happened.