Fixed! How Can I Stop Nextbestgame.org and Zebragamers.org Pop-up Completely - Removal Guide

Malware site "nextbestgame.org" goes undetected. Pops up in Firefox on each reboot.Every time I power up or restart my computer, the website nextbestgame.org immediately floods my screen in the form of three Firefox popup windows.  For example, it was something like "Zebragamers.org" previously. It makes it very difficult to Google the problem because of the name changes.

Information of Nextbestgame.org and Zebragamers.org