We have received reports from many users who were interrupted in their browsing experience and who got redirected to a fake page purporting to provide an "urgent update" and prompting to download a firefox-patch.js (or .exe) file. This is a scam tactic trying to trick you into installing malware!

To our knowledge those notices are a form of "malvertising": those fake notices get triggered by code contained in ads that are displayed on otherwise legitimate websites you are visiting and get spread through advertisement networks. This is an example how such a fake update notice may look like - they are hosted on randomly generated and quickly changing domains:

What you can do if you spot a fake update notice?

1. Never save and open/run unsolicited files!
2. Install an ad-blocking addon from addons.mozilla.org to avoid such kind of malvertising in the future.
3. Report web forgeries to the Google Web Forgery site.

What you can do to prevent malware on your computer

1. Run a malware scan on your computer to make sure your computer was not infected. (See Troubleshoot Firefox issues caused by malware.)
2. Avoid downloads from unreliable sources in the future.

To learn more about malware

• Kaspersky Internet Safety
• AVG "Is it Malware?"
• Apple Forums advice on if you have malware

Although we cannot root out every bad actor on the web, knowing how to recognize and report such frauds helps us keep the Internet open and safer.