Thank you for sharing your browser details, which appear to the right of your post under Question Details > More System Details. If you check your extensions, you can see that you are infected with "Searchme" and you need to remove it. Open the Add-ons page using either: * Cmd+Shift+a * "3-bar" menu button (or Tools menu) > Add-ons In the left column, click Extensions. Then on the right side remove or disable Searchme. ''Bear in mind that all extensions are optional and none are included with Firefox when you first get it.'' Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step. Does that help you regain control? This might be the tip of a malware iceberg. When you install free software, you often get unmentioned bundled extras. I don't know how best to "clean" a Mac of such items, but you may want to look into it.