Hi ! To remove that malware : 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 Windows Control Panel. 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.