Firefox updates itself but automatic update is switched off in settings

Firefox periodically updates itself without my initiation or confirmation, but automatic update is switched off in settings. Some of similar questions I've found and checked settings: Type in the address bar about:config (press Enter) (promise to be carefull, if asked) Type in the search box : app.update Then look for the preferences : app.update.auto app.update.enabled app.update.silent and set their values to false

All are set to false. My settings does not allow automatic update. Why updates happen automatically?