This might surprise you:
(A "How To") Did you know that, even if you don't use it, an un-maintained web browser installed on your system can be a serious security risk? Just having it installed on your system can give an attacker a possible access for breaking into your computer or exploiting your computer's internet conection and bandwidth. If you have a browser installed on your computer that you do not use, you have three choices:

1. Remove it completely from your system (does not apply to Internet Explorer on any Windows as the browser is integrated with the operating system.), 
2. Constantly update it with the latest version, security fixes and patches, and 
3. Set all of the security settings to the highest possible level and deny all cookies.