You're right, it's malware. To others who might find this thread: '''Do not open that file.''' ''If you did open it, run Malwarebytes Anti-Malware and your choice of other clean-up tools listed here:'' [[Troubleshoot Firefox issues caused by malware]]. It's part of a longstanding pattern, unfortunately. The redirects to the malware distribution sites are believed to be delivered through ad networks on popular sites. You could consider using an extension to block ads, such as: [https://addons.mozilla.org/firefox/addon/ublock-origin/]. Also, see: [[I found a fake Firefox update]].