Tab stopped working in Firefox

Just mysteriously overnight.. used to work just fine. The problem persists on all pages I’ve visited, restarts made no difference. No upgrades has happened in the mean time that I know about. Seems like I’m not alone.

UPDATE: I don’t have the specific extension mentioned in that forum post but I uninstalled a few old extension that I still had floating around, restarted firefox and voila, problem cured.