While browsing IMDB on Fantastic Beasts (http:// www . imdb . com/title/tt3183660/) I clicked on Full Cast and Crew(http:// w ww .imdb . com/title/tt3183660/fullcredits?ref_=tt_ql_1) and then on Ezra Miller (http:// www . imdb . com/name/nm3009232/?ref_=ttfc_fc_cl_t12). After a few seconds the Orange Scam screen "Urgent Firefox Update" pops up. See attached screen capture which shows the URL to which I was sent and the script file it wanted me to download. How come Norton 360 doesn't catch and block this?
Firefox 50.0 for Windows.
OS Name Microsoft Windows 10 Pro
Version 10.0.14393 Build 14393

It is not malware so to say. It is a fake webpage trying to get you to install a fake java plug in. This practice is not uncommon. Do you have Firefox's security turned on? Google Chrome has security built in which blocks malicious webpages and phishing attempts. I also see you are not running an adblocker nor do you seem to have Firefox's popup blocker turned on. I highly recommend you install uBlock Origin extension and reset your Firefox to the default status.
https //mahseeksperttv - upgraded, huhh? I

Norton does not catch or block this because it is caused by JavaScript, likely contained in an advertisement on a webpage you were viewing. The sites to which victims are redirected change frequently, so it is almost impossible for security products to know which sites are currently hosting the malware.
The way to avoid this situation in Firefox is to use the NoScript add-on, which blocks JavaScript globally, permitting it to run only on sites that you specifically allow.