How do I open and install this file: firefox-patch.js

'''You don't install that js file!''' That is a fake update. malicious file that would install malware or worse if you ran it. Stuff like that has floating around for 3 1/2 months now, being "offered" by compromised advertising networks. And this "bad player" is proving difficult to stop; multiple new domains cropping up daily, so by the time he is discovered he has moved on to a new domain. Here's a thread about this guy's "travels": https://support.mozilla.org/en-US/forums/contributors/712056 Mozilla doesn't use "firefox-patch" files, neither .exe nor .js. When Mozilla wants to "patch" Firefox, it installs a minor update like the Firefox 47.0.1 update. There are currently no updates being issued for Firefox 48.0.