Removing the extension is just part of the damage, they also change your default from the location bar. See https://support.mozilla.com/questions/850287 Avoiding the problems: Many software installations contain additional baggage known as crapware. The Yahoo Toolbar is packaged with Java. More information on ask.com, Yahoo Toolbars which involve extensions, not just changes to the home page. *http://kb.mozillazine.org/Problematic_extensions *Uninstalling toolbars - MozillaZine Knowledge Base *:http://kb.mozillazine.org/Uninstalling_toolbars *More information on configuration variables available in about:config entries and for users not familiar with the process there is about:config (How to change).