Netstat shows loopback IP from FF PID

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Post Posted May 15th, 2017, 8:45 pm

Howdy folks, first post, and my reason for being here.

I've done the web searches already, and I don't see an answer that satisfies me yet.

In my netstat, before connecting to any web site, there are 2 connections to my localhost from ports being run by FireFox.

Before you ask my version, I will tell you that K-Meleon, also produced by Mozilla, has the exact same behavior. So no need to ask about add-ins, version, etc. This is a universal deal.

From the KB on this site: ... p_(Firefox)

which refers us here:

That was the first link I found, and it doesn't answer the question at all. It just marks it as won't fix, but doesn't explain what it's for.

NSPR pollable events are implemented with a pair of
TCP sockets on Windows. Unfortunately this requires opening
listening sockets on the loopback address temporarily.

I don't know how to implement NSPR pollable events
on Windows without using a pair of TCP sockets, so I am
marking this bug WONTFIX.

crawdad wrote:No other browser does this. A browser should NOT require server rights to operate.
Since unruly behavior is HIGHLY undesireable and will cause SOME folx to mistrust mozilla.
Justifiably so.

Leaving this bug as "resolved/wontfix" is WRONG!
In this age of paranoia, it should be obvious that this is undesireable behavior.

15 years ago, somebody said that.

And then in 2009: ... -ports-why

Arjan wrote:TCPView and ZoneAlarm firewall reveal that Firefox is accepting incoming connections on two ports on localhost ( The port numbers are not fixed.

I reinstalled Firefox without any add-ons, and scanned using 3 antivirus programs (Avast, AVG and Norton), but Firefox is still listening to two ports. Other browsers such as Opera, K-Meleon, IE and Safari do not behave like this.

If it's true that K-Meleon didn't have this in 2009, even though I can attest that it does today, that means this functionality was deliberately added.

This then gives me pause with regard to my final quote, which is where my inquisitiveness on this matter stems from. Odin's Eye?


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Post Posted May 16th, 2017, 3:37 am

Firefox uses a loopback address to communicate with its Password Manager.

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Joined: December 30th, 2009, 11:25 pm

Post Posted May 17th, 2017, 9:47 am

The first quote in your post seems to answer the question of the purpose of the open ports definitively. Any further questions as to why pollable
events are used as opposed to some other method of program internal communication would surely be classified as rather esoteric systems
programming issues hardly suitable for a forum such as, which Mozilla developers are not known to frequent.

There seems to be a great deal of uninformed FUD in the commentary on this subject. Anyone who imagines there are security concerns should
actually read the followup bug by the Mozilla developer who marked the original bug WONTFIX.

K-Meleon is NOT "produced by Mozilla", although it uses software components provided by Mozilla, just like quite a few other independent browsers.


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Post Posted May 17th, 2017, 1:36 pm

Star_Scream wrote:Before you ask my version, I will tell you that K-Meleon, also produced by Mozilla, has the exact same behavior. So no need to ask about add-ins, version, etc. This is a universal deal.
What is K-Meleon?
K-Meleon is an extremely fast, customizable, lightweight web browser based on the Gecko layout engine developed by Mozilla which is also used by Firefox. K-Meleon is free, open-source software released under the GNU General Public License.

more history of K-Meleon is at

The only desktop web browser for Windows, Mac OSX, and Linux that Mozilla makes is the Firefox you can download from

SeaMonkey also uses the Gecko engine like Firefox however it is made by a community and not Mozilla.

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