Firefox uses Inter-Process Communication (IPC) to implement privilege separation, which makes it an important cornerstone in our security architecture. A previous blog post focused on fuzzing the C++ side of IPC. This blog post will look at IPC in JavaScript, which is used in various parts of the user interface. First, we will briefly revisit the multi-process architecture and upcoming changes for Project Fission, Firefox’ implementation for Site Isolation. We will then move on to examine t...