The site primarily responsible for the rapid spread of Mozilla's Firefox browser, appropriately called SpreadFirefox, was hacked. The site has been the main hub of the grassroots marketing effort that has led to Firefox steadily gaining marketshare against corporate browsers such as Microsoft's Internet Explorer. User data may have potentially been exposed or the site's server used to send spam. It's only those who have used SpreadFirefox who need to be concerned about their data and they have been urged to change their information.