As a follow up... I just uninstalled Firefox, which made no difference so I deleted the entire Mozilla folder from my user account (under AppData that contains my Firefox profile folder(s). This too, made no difference.

WTF? Is Firefox keeping this dang extension in my Sync account?

When an application such as Norton Security Suite installs an extension for Firefox, the user needs to remove that extension thru that application that installed it. Otherwise it will just keep reappearing.

As far as Sync goes, it doesn't synchronize the users actual own extensions it installs the users extensions afresh from the Addons.Mozilla/Org server. So considering that Norton supplies the extension and it's not available from Mozilla, Sync wouldn't be "reinstalling" it.

But there is no Norton Security Suite installed, nor the Norton Security Toolbar. I obviously installed it at some point in the past as, under "more info", Firefox says the extension was last updated on June 17th 2017. But I uninstalled the toolbar and the other Norton Security Suite crap.

Does this mean that Firefox is helpless against an extension that "wants" itself installed? Wouldn't that be an open door for a malicious extension?

Then you need to go and download the norton removal tool from their site to cleanup norton.

Then how did that Norton Security Toolbar get installed to begin with? Firefox add-ons wouldn't show that extension if it wasn't sitting on your hard drive where Firefox found it. And the Registry key that pointed Firefox towards that extension wasn't still in the Registry.

If you removed a Norton Security Suite (or whatever-named Norton app which originally installed that Toolbar extension) in the past you may need to use a Registry cleaner application to remove all traces of the Norton program or do a manual cleaning. Then the mere presence of that extension shouldn't be "seen" by the Addons Manager.

"Then how did that Norton Security Toolbar get installed to begin with? "

As I said:

"I obviously installed it at some point in the past as, under "more info", Firefox says the extension was last updated on June 17th 2017. But I uninstalled the toolbar and the other Norton Security Suite crap."

Forgive me but, I still don't understand. Why is Firefox at the mercy of a 3rd party extension? If Firefox can "disable" the extension why does it not have the ability to delete, or at least, remove it from the Firefox's extensions menu?

Most A/V companies have a 'remove' all traces of their software utility.

Norton and MacAfee are such a pain to remove they are considered almost virus's themselves!

stoc2528 said

Forgive me but, I still don't understand. Why is Firefox at the mercy of a 3rd party extension? If Firefox can "disable" the extension why does it not have the ability to delete, or at least, remove it from the Firefox's extensions menu?

Firefox just shows what the Windows Registry indicates is installed and available for Firefox to use, even if the add-on was left behind when the program that originally installed that add-on was removed.

With the similar issues that I have had with Norton applications over the last 25 years, that happening was regular occurrence until I said "never again" and started staying clear of Norton apps. Been going downhill since 1990 when Peter Norton sold the company to Symantec.

Personal note : With Windows' built-in Defender and the safest browser on the planet :  to me it feels like being in Fort Knox   !

See : http://tech.firstpost.com/news-analysis/ex-mozilla-firefox-developer-says-anti-virus-software-does-more-harm-than-good-359798.html

And also :
https://www.howtogeek.com/239950/dont-use-your-antivirus-browser-extensions-they-can-actually-make-you-less-safe/

Yeppers,

I agree, it!s also bloatware and a system resourceshog.