Finally decided to join because this issue has me stumped. The main question is whether or not the problem is malvertising or an actual virus, and I have explained the situation below:
So in the past week I have started getting the "Firefox-patch.js" popup whilst browsing the interweb using Firefox. I am a very careful browser, with no add-ons at all, and I only go to reputable sites. Sometimes even the most careful user can get a virus, so whenever I have a hint that my machine might have an infection of some sort, I simply reinstall from a system image that I keep on a separate drive. (I create the system image from scratch; I install Windows 7 Pro, completely install all updates, install all my applications, setup/tweak the system how I like it, and then pull the system image down to my external drive). This practice has fixed my problem every time I have ever used it, but this time it didn't.
I reinstalled from the system image, but several hours later the popup happened again. I am now wondering if my system image is itself infected, or if this is just some type of ad-malware. If it is adware, that would explain why it still happens after the re-install, but I am not sure. MSE scanning didn't find anything, nor did Malwarebytes.
Others have suggested using an adblocker and seeing if that helps, and I might give that a try, but I can't help but worry that this might simply mask the problem (if it's a virus), not eliminate it.
So what do you guys think? Is my system image still a safe restore point? I tried to explain the situation as best I could, but ask questions if I need to clarify anything