Hi, Even though Yahoo is a legitimate search engine - it sounds like you're dealing with Yahoo.search.com Redirect virus, malware that you will of course want to get rid of. Go to the 3-bar menu (or 'Tools') => Addons => Extensions and look for '''any unfamiliar or suspicious looking extensions'''. When you find any : remove them. Do the same in your system's Control Panel and look for anything suspicious. However : most malware will be 'hiding' somewhere , so let's run malware scans : Further information can be found in this article : https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no '''Run most or all of the listed malware scanners'''. They all work differently - what one program doesn't pick up, the other might. Also see : https://www.pcrisk.com/removal-guides/8835-search-yahoo-com-redirect