Firefox doesn't display a Remove button for an extension if it was installed into a "shared" location (that is, not in your currently active profile folder). Often in that case, there is an entry in the Windows Control Panel, Uninstall a Program, which lets you remove it. You can click the Installed on column heading to sort by date and see whether you can spot it based on the approximate install date.

If that doesn't work, there is a somewhat arduous way to discover the location of an extension on disk so you can remove it.

Open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter/Return

In the first table on the page, click the "Show Folder" button. This should launch a new window listing your settings files.

Scroll down and find extensions.json and make a copy somewhere convenient, such as your Documents folder. You can close out of the Windows Explorer window after that.

Back in Firefox, open that copy of extensions.json in Firefox's "Scratchpad" tool as follows. Launch the Scratchpad from the Developer menu, either:

• "3-bar" menu button > Developer > Scratchpad
• (menu bar) Tools > Web Developer > Scratchpad

Use the Open button on the Scratchpad's toolbar to open the backup copy you made of extensions.json and then click the Pretty Print button on the toolbar to re-layout the data in a more readable format.

Then use Find (Ctrl+f) to search for some part of the name of the unwanted extension, and you should see various information about it. The descriptor gives its location on disk. (The \ in Windows folder paths is doubled in this file due to the way it is processed. When exploring your disk, read \\ as \.)

Can you track it down? That may help you discover an uninstaller in the Control Panel, or you can potentially delete the extension from disk. Extensions can be a single .xpi file, or a folder of files and other folders. If you're not confident about what you find, let us know what you see.

Note: you don't need to save the changes to the file when you close the Scratchpad unless you want to keep the "pretty" version for future reference.

Thanks for the reply.

C:\Windows\Microsoft.NET\Framework\v3.5\Windows Presentation Foundation\DotNetAssistantExtension

This looks like a regular Microsoft .net framework update location that could be created. I am not sure if I should delete it.

These are the contents:

Folder - chrome - chrome.jar Folder - defaults - preferences - defaults.js chrome.manifest install.rdf MicrosoftDotNetFrameworkAssistant.xpi

So I think that Google Chrome browser might need these files and this extension?

If I do delete this folder, should I just delete the whole thing?

Thank you.

Hi SyncroScales, when you are examining the interior contents of a .xpi file, the word "chrome" refers to Firefox's user interface. It's a term Mozilla has used for a really long time; another company liked it so much they used that term for a browser and and operating system.

If you are uncomfortable deleting the .xpi file, you can just leave it disabled.

Hello jscher2000.

I moved the xpi file onto my desktop, and the add-on is still in the add-on section of Firefox. Does it have to be deleted off the computer completely?

I closed and restarted Firefox also.

I don't think I should delete/uninstall Microsoft .NET Framework v3.5 SP1 from my computer in Control Panel - Programs and Features. Isn't this a needed program?

The Microsoft .NET Framework Assistant extension is a malicious extension that is distributed under the same name to trick users into installing it, and turns users into a botnet that conducts SQL injection attacks on visited websites.

It was added to blocklist back on December 16, 2013.

https://addons.mozilla.org/firefox/blocked/i508 https://addons.mozilla.org/firefox/blocked/

SyncroScales said

Folder - chrome - chrome.jar chrome.manifest So I think that Google Chrome browser might need these files and this extension?

As said any mention of chrome in Firefox has nothing to do with the Google Chrome browser that came out pretty much six years after the browser we know as Firefox (was Phoenix and Firebird early on) did and was in use in Mozilla code for years before.

https://developer.mozilla.org/en/docs/Chrome_Registration

Chrome is the set of user interface elements of the application window that are outside the window's content area. Toolbars, menu bars, progress bars, and window title bars are all examples of elements that are typically part of the chrome.

See https://support.microsoft.com/en-us/kb/963707

SyncroScales said

I moved the xpi file onto my desktop, and the add-on is still in the add-on section of Firefox. Does it have to be deleted off the computer completely?

Where did you find the file?

If Firefox can still "see" it in the new location, it seems one of these might explain that:

• Firefox hasn't updated extensions.json yet (did you already exit Firefox and start it up again?)
• Firefox is aware of another copy of the file that hasn't moved
• the Windows registry updated to point to the new location (seems unlikely)