When I looked at this last August, bing''.''vc was a site operated by Beijing MSYT Technology Co., and had no relationship with Bing from Microsoft. In a thread on another forum, they had to go to extraordinary lengths to remove the malware that keeps modifying the system: http://forums.mozillazine.org/viewtopic.php?p=14290001#p14290001 You could try the standard scanning/cleaning tools in our support article "[[Troubleshoot Firefox issues caused by malware]]". If those do not work, you could try the malware cleanup forums listed in the article. See also: [https://malwaretips.com/blogs/remove-bing-vc/ How to remove Bing.vc hijack (Virus Removal Guide)] Can you get rid of it?