Late last week, Mozilla published an update that broke every add-on or extension to Firefox. The certificate they used to verify that add-ons were correctly signed expired. When Firefox updated, every add-on or extension was considered unsafe, and disabled. They have published a fix or two over the weekend, and most people should be back to normal.
The reporting of this as a "security update" is rather misleading. Actually, in the name of security it was broken in the first place, since the add-ons couldn't be verified. If you use things like NoScript to enhance your security, NoScript was blocked and that may have become a security issue. However, that does not make the update to correct the certificate a security fix. Let's not fall to the lure of sensational headlines. But really, did they get you to click on the article?