How extensive is the invasion? For example, are you able to: * Gain control of your startup page and change it to a new home page? See: ** [[Startup, home page, tabs, and download settings]] * Select your own preferred default search engine and have Firefox use it? See: ** [[Change your default search settings in Firefox]] If your choices get changed back or are overridden, a common explanation would be a bad add-on or external malware. Here's my suggested procedure for tracking down and cleaning up bad add-ons and other hijackers. I know it seems long, but it's really not that bad. (For Windows Vista, 7, 8, 8.1, 10; XP is somewhat different) (1) Open the Windows '''Control Panel''', Uninstall a Program. After the list loads, click the "Installed on" column heading to group the infections, I mean, additions, by date. This can help in smoking out undisclosed bundle items that snuck in with some software you agreed to install. ''Be suspicious of everything you do not recognize/remember, as malware often uses important or innocent sounding names to discourage you from removing it.'' Take out as much trash as possible here. (2) Open Firefox's '''Add-ons page''' using either: * Ctrl+Shift+a * "3-bar" menu button (or Tools menu) > Add-ons * in the Windows "Run" dialog, type or paste <br><code>firefox.exe "about:addons"</code> In the left column, click '''Plugins'''. Set nonessential and unrecognized plugins to "Never Activate". In the left column, click '''Extensions'''. Then, if in doubt, disable (or Remove, if possible) unrecognized and unwanted extensions. ''All extensions are optional; none come with Firefox.'' 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. Any improvement? (3) You can search for remaining issues with the '''scanning/cleaning tools''' listed in our support article: [[Troubleshoot Firefox issues caused by malware]]. These on-demand scanners are free and take considerable time to run. If they finish quickly and especially if they require payment, you may have a serious infection. I suggest the specialized forums listed in the article in that case.