You found one of several FAKE websites with a MALICIOUS "patch" that are completely unofficial. Unfortunately, they are abusing the Firefox logo without permission and fooling users like you. Hopefully Malwarebytes protected you fully from this dangerous .js file. If you have any suspicions that it might have executed, I'd post about it on the Malwarebytes forum since they are likely to be able to help. Now... if you wouldn't mind, could you report the bad site here to help get it added to Firefox's phishing/malware filter: https://www.google.com/safebrowsing/report_badware/ And, sorry! People ''are'' trying to figure out what to do about this.