First about Java : it 's not supported (anymore) in Firefox. See : https://support.mozilla.org/en-US/kb/npapi-plugins If, however, you do have Java installed on your system, please see : https://java.com/en/download/help/linux_uninstall.xml As for Flash : Your system details doesn't show whether you have Adobe Flash installed on your system - in Firefox it's called 'Shockwave Flash' and you would find it in Add-ons => Plugins. If you do see it there, you can set it to 'Never Activate', when you're sure that's what you want to do. If you keep Adobe Flash up to date , you don't need to be concerned about security. See : https://support.mozilla.org/en-US/kb/install-flash-plugin-view-videos-animations-games