Taking a Screen shot; Windows > Start > search box > Snip. Select Snipping Tool. Use a compressed image type like PNG or JPG to save the screenshot. Save the picture(s) to your desktop. Now look at the Reply box below. Press the button under it that says Browse. Now select the screenshot(s) from the desktop and load them one at a time.

On the original post, the browse function kept going without uploading the images, but for some reason it is allowing me to attach them now. Anyway, here they are.

Starting with Firefox version 48, the add-on signing requirement will be enforced with no override in Release and Beta versions of Firefox. See the MozillaWiki article, Add-ons/Extension Signing for more information.

I have been looking for Mozilla Firefox Extension 1.0 but can't find it anywhere. Where did you find it?

That sounds like some malware. I assume it doesn't have a Remove button or you would already have gotten rid of it. There is a somewhat arduous way to discover the location of an extension on disk so you can figure out what program it's under, or just delete 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.