Http://s.mgkaxjfwfc.com hijacks YouTube pages

Using Firefox, YouTube addresses periodically get forwarded to an address like http :// s.mgkaxjfwfc.com/s73bc5wskpmgwwcowokg0w0os4 -

 

The forwarding page is blank but the code appears as though they are attempting to show my intended page in an ifram

 

I figured it came with Privatize VPN but have since deleted it and I have run a complete Full Scan with latest updates and it still happens. How do I get rid of this?

 

 

 

 

[Edit: Removing hyperlink to a potentially malicious website to conform with the Participation Guidelines and Terms of Service]