That is an extension, and there probably is an entry in the Windows Control Panel. Let's start there. Start menu > Control Panel > Uninstall a Program Click the "Installed on" column heading to group by date and you should be able to find whatever extras were installed along with FileZilla and remove them. And anything else suspicious. Then exit Firefox (if it's open) and start it up again so that it re-reads available extensions, and check the Add-ons page. Either: * Ctrl+Shift+a * orange Firefox button (or Tools menu) > Add-ons In the left column, click Extensions. Then disable/remove everything that doesn't sound familiar and useful. Usually 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. Finally, to reset your new tab, home page, and default search provider to Firefox defaults, you can use this extension: https://addons.mozilla.org/firefox/addon/searchreset/ Cured? Probably not a bad idea to run some supplemental security scans. This article lists tools other Firefox users have found helpful: [[Troubleshoot Firefox issues caused by malware]].