-install-global-extension doesn't work in Firefox because the extension name is being turned into a URI. From strace output: 10875 execve("/usr/lib64/mozilla-firefox/firefox-bin", ["/usr/lib64/mozilla-firefox/firef"..., "-install-global-extension", "file:///root/firefox-extension Reproducible: Always Steps to Reproduce: 1. /usr/bin/firefox -install-global-extension /tmp/xxx.xpi 2. ??? Expected Results: /usr/lib64/mozilla-firefox/extensions should have the extension The problem can be worked around by calling firefox directly instead of the /usr/bin/firefox wrapper. This syntax works: /usr/lib64/mozilla-firefox/firefox -install-global-extension /tmp/firefox-extensions/torbutton-1.0.4.01-fx+tb.xpi
mozilla-launcher will be deprecated