According to the system details that are included in your question, it appears that you are running the most recent version of Firefox. This is a scam.

Please refer to this Mozilla support article to find out how to remove this scam:

• Troubleshoot Firefox issues caused by malware

Did this fix the issue? Please let us know.

Firefox 42.0 is still the current Release from mozilla.org

Firefox updates are done in Firefox itself or by download from mozilla.org or www.mozilla.org/firefox/all whether on Windows, Mac OSX, or Linux.

Mozilla does not advertise or distribute updates in random sites or popups.

Thank you for your replies. I did think it was a hoax/scam/spam after the alert went up so I never installed the download - deleted it and then ran MalwareBytes as well as SuperAntiSpyware and there was no infection found.

Cheers,

jeff

. Whenever you get a message / popup that software / files need to be updated;

DO NOT USE ANY OF THE PROVIDED LINKS

While this may be a legitimate message, it could also be Malware or a Virus. Any time you want or need to check for upgrades, go to the web site of the True Owner of the program in question. For example, to check out Firefox, go to Mozilla.org. {web link}

You can also report such a site at; Google Report Phishing Page {web link} which is the same when done while on site by going to Help > Report Web Forgery

Help us safeguard Mozilla’s trademarks by reporting misuse {web link}

jeff_janni said

Thank you for your replies. I did think it was a hoax/scam/spam after the alert went up so I never installed the download - deleted it and then ran MalwareBytes as well as SuperAntiSpyware and there was no infection found.

Does this mean that you are still having the issue?

From my own personal experience, I've found that AdwCleaner is the best at locating infections that the other free software cannot. I would recommend downloading and running AdwCleaner.

Let us know if this fixes the issue.