The auto-update feature of Firefox does work in Linux but only for root (or probably, also for someone with write-access). This means that as soon as we learned that Firefox was updated, we should run Firefox as root and auto-update it (Help>Check for updates). Browsing as root, except for updating, is still strongly discouraged. Also, note that the updater will ask to restart Firefox. Do not select restart if you used sudo to run it.