If you get a pop-up message asking to update Firefox or plugins or scanning for malware then such a message is likely a scam and you should never respond to such an alert to avoid getting infected with malware.

• Only update Firefox via "Help > About" or by downloading and installing Firefox from the Mozilla server and never via a pop-up or link on a web page.
• plugins should only be updated via the plugin itself or by visiting the home page of the plugin.

You can find the full version of the current Firefox release (47.0.1) in all languages and all operating systems here:

• https://www.mozilla.org/en-US/firefox/all/
• https://www.mozilla.org/en-US/firefox/notes/

Please let us see a screenshot.

• How do I create a screenshot of my problem?

It is probably malware, and may be because you already have malware on your computer.

It may be a good idea to scan your computer for malware. I suggest you use all the tools mentioned in this article

• Troubleshoot Firefox issues caused by malware

You may find using blockers means you will see less of this type of problem

• Consider something such as https://addons.mozilla.org//firefox/addon/ublock-origin/