Hi, open the 3-bar menu > Add-ons > Extensions, then look for and remove/disable anything you don't recognise, especially anything with 'search' in its name. Restart Firefox afterwards. Go to the 3-bar menu > Preferences > Search, and make sure there aren't any unusual Yahoo search engines - you can select then click the Remove button if necessary on anything dubious. Look for any recently installed programs on your Mac that you don't recognise: [[What is search hijacking?]]. ''If your question is resolved by this or another answer, please help other users by marking the best reply as Solved. Thank you!''