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.

The official Firefox updates has not changed since Firefox 1.5 as it is still internally patches in Firefox (with a .mar file that nobody sees) or by download from mozilla.org www.mozilla.org/firefox/all/

Mozilla has no need to host any Firefox downloads or updates elsewhere, especially not a random weird name websites registered only within a day.

So please do not try to run this fake firefox-patch.js file.