http://jqyzxhjk6psc6ul5jnfwloamhtyh7si74b4743k2qgpskwwxrzhsxmad.onion/docs/torbutton/en/design/index.html.en
These are: network.security.ports.banned Torbutton sets this setting to add ports 8123, 8118, 9050 and 9051 (which it
reads from extensions.torbutton.banned_ports ) to the list
of ports Firefox is forbidden to access. These ports are Polipo, Privoxy, Tor,
and the Tor control port, respectively. This is set for both Tor and Non-Tor
usage, and prevents websites from attempting to do http fetches from these
ports to see if they are open, which addresses the Tor Undiscoverability requirement....