I think it is a bug. It was in version 55 though. It is a legitimate Firefox File and be looks of message a security setting is stopping it from pinging the Mozilla Servers at shut down.

It would seem you need to ok that file/action in what ever security program/firewall you are using.

I would think that would be the solution. The other option is to uninstall 56 and download A Full Installer Version 56.0.1 https://www.mozilla.org/en-US/firefox/all/ This may or may not help.

Please let us know if this solved your issue or if need further assistance.

Well, I'll add more to this error as I put Firefox through a refresh and then closed out Firefox with the virgin screen of Firefox...voila, no Windows error. So then I went in to customize my toolbars and home page to get it the way i want it to be...bummer, Windows error message returned for address C:\Program Files (x86)\Mozilla Firefox\pingsender.exe.

I really don't want to or know how to back update 56.0.1 as I believe all of this started with it.

May have started with that but it is a Windows Error as you say. Going back is not a solution as you will only have to update and also do not want to miss the release of Firefox 57 Quantum Nov 14th. https://www.mozilla.org/en-US/firefox/quantum/

Though a large number of people are having issues with Microsoft not supporting Win 7 as they should to support changing tech as well as standards and rules set by the W3C (web browsers, web page codes ect) They are going to the Extended Release Version : https://www.mozilla.org/en-US/firefox/organizations/

It has been to long since I have run Win 7 to remember security for it. So as it is a windows issue you can go to MS windows forums or to https://www.sevenforums.com/ to help you change that setting.

Please let us know if this solved your issue or if need further assistance.