Browser Hijacker attacks your computer to hijack the option of the browsers. Their main target is to serve ads. So they hijack homepage, new tab, and default search engine and set these addresses to a specific page to display ad. You cannot change these options. You need to take extra help. Here in this video, you will know the manual and automatic method to remove any browser hijacker from Mozilla Firefox.
MalwareFox- https://www.smartpcuser.com/remover