Firefox is listening for incoming connections on two ports. Why?

"These are local loopback ports. Firefox uses them for local communication.

A loopback connection (to IP address 127.0.0.1) can be made by Firefox on non-Unix machines. In this case the browser is communicating with itself as expected, and it is not recommended that this communication be blocked.

Take a look at this: Connections established on startup - Firefox

And the bug report ""Connections opened on loopback (127.0.0.1) show in NETSTAT and ZoneAlarm has ""server rights"" alerts"" explains:

Whenever Mozilla is running there are two connections to the loopback address
that are connected to each other. The ports change but they are usually
lower-numbered unregistered ports."