You may have a program on your system talking to that site. Check your add-ons.

Disabled all add-ons. Still have the problem.

First question: Why can't I delete add-ons like in previous editions?

Second question: Microsoft Office installs two add-on into FF without my permission.

I uninstalled FF. All FF files were deleted including profile. While sorting through the Registry I found where Microsoft Office installs add-ons to all NPAPI browsers as part of their authorization validation. There is nothing in Office that should have anything to do with FF. Why does FF permit add-ons from any other software package to circumvent FF add-on controls? Is FF paid to do this for Microsoft? How do FF users get control of all add-ons.

There are two types of Add-ons. There are the Extensions that you find and install. And there are also Plugins. These are from other programs that are on your system when Firefox starts. Like video players, anti-virus, and many more. You can disable normal Add-ons by going to the Add-ons Manager,

2nd Q: In Firefox 43 those Office add-ons would probably be blocked if they are "Extension" type Add-ons- whereas Plugins (also classified as Add-ons) aren't actually installed into Firefox. I have never used Office, I went from Word Perfect to Open Office, then to Libre Office, and only Open Office installed any Plugins for Firefox - but they were useful, but that was a few years ago and I can't remember what they were used for. But I do remember turning the the "NPAPI Plugin" on in Open Office.

Plugins just sit where their installer places them on your hard drive, and provides "bread crumbs" in the Registry so that Firefox can find Plugins. You can see the "path to" where each Plugin is sitting on the hard drive in the about:plugins window inside of Firefox.

Firefox has no use for Plugins itself, the Plugins are there for other applications that may need Firefox for their functionality; and some programs install Plugins just because they can. '(Like the Google updater appearing in Firefox under Plugins ... Firefox has its own "updater" and nothing actually "in" Firefox should need it either, but it's there if you installed Google Chrome.) Overall, that is how the Plugins system works in Windows operating systems and the programs that get installed to Windows OS's.

1st Q: That isn't part of Firefox and probably not via any extensions that you installed from AMO. Add This is a social networking setup of some sort, that earns their living by selling data that they collect. The web pages that you visit probably have an agreement with Add This to carry Add This code on their webpages to earn that website some money or other consideration. And that what I believe you are seeing - data about "you" being sent to Add This. That allows Add This to track your "travels" and types of websites that you visit and categorize that data before they sell it. Firefox does have "Tracking" protection - https://support.mozilla.org/en-US/kb/settings-privacy-browsing-history-do-not-track - but IMO that relies upon voluntary compliance. And I don't trust any damn "social" website to voluntarily comply with any damn thing. And I ain't a sociable type guy.

Adblock Plus and the "Social" filterset can block that "social code" from loading into the browser as part of the webpage, which should shut down the tracking and probably that "sending" of data. I block it with the NoScript extension, which is a pain in the ass to get setup initially.

the-edmeister,

Your information was very helpful but I wanted to get to the source and found it! Mozilla is not off the hook on this but a co-conspirator or has a sloppy approval process to get an add-on signed.

I made two virgin installs of Windows 7. Added Systeminternals and monitored traffic. No calls to Addthis. Microsoft office was added to one machine which immediately began message traffic to Addthis.

Microsoft has the major blame in this contact to this malicious website that tracks information and sells to other businesses. But Mozilla should never have signed the Microsoft plug-ins when their code initiates contact to a known malicious site.

Another interesting observation is that Microsoft updates their software using SSH Tunnesl which bypass Windows Firewall and any internet security software. What a software vulnerability for hacking!

The fix for this problem can be done at least two ways. A single line in the "Host" file takes care of it for one machine. A firewall block for Addthis.com in the modem takes care of all the machines until changes are mode to tunnel this information out.

I thank you for your help in getting me to the root cause. This topic can be closed.