Centos replaced well-running customise Firefox with version ESR 45.1.0 * All the add-ons (language dictionaries, Adblock Plus, Classic Theme Restorer etc.) were disabled with no simple method of reactivating them. Reason given was they were "unsigned". * About:config xpinstall.signatures.required = false partially reduced the problem. * Then possible to reactivate some disabled add-ons, but others down-loaded OK but would not install * removing files in ~/.mozilla/firefox/.../extensions.* and restarting was supposed to help However the time-wasting problem remains, so too do the down-loaded extensions in /tmp, example tmp-xxx.xpi Would be really nice if Centos warned its loyal and grateful users of possible problems before those users trustingly replaced working programmes with considerable time-wasting problems. Time spent on trying to return Firefox to a useful and dependable working tool is unavailable for other tasks :-( -- Regards, Paul. England, EU. England's place is in the European Union.