In August, Mozilla was notified by security researcher Cody Crews that a malicious advertisement on a Russian news site was exploiting a vulnerability in Firefox’s PDF Viewer. The exploit payload searched for sensitive files on users’ local filesystem, and reportedly uploaded them to a server in Ukraine.
I am proud to say Firejail users were protected! The default Firejail configuration blocked access to .ssh, .gnupg and .filezilla in all directories present under /home, while more advanced configurations blocked everything else.
The main focus of Firejail project is GUI application sandboxing, with web browsers being one of the main targets. I will describe some of the new features available in Firejail, and how to use them to sandbox a web browser such as Mozilla Firefox.
A short note before we start. By default, Firefox browser uses a single process to handle multiple windows. When you start the browser, if another Firefox process is already running, the existing process opens a new tab or a new window. Make sure Firefox is not already running when you start it in Firejail sandbox.