Hi   ! If you have deleted Yahoo Search everywhere, chances are that we're not dealing here with the legitimate Yahoo Search engine, but with search.yahoo.com which is a browser hijacker. If this is the case : Go to the 3-bar menu => Addons => and look for any unfamiliar or suspicious looking extensions, like e.g.: SafeSearch Incognito SearchAssist Incognito When you find any : remove them. Also look in : Advanced => Network tab => Under : 'Offline Web Content and User Data' Do the same in Windows' Control Panel => Programs. 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://malwaretips.com/blogs/yahoo-toolbar-removal/

Many thanks for help, will work my way through those solutions