Introduction Flatpak promises a secure runtime for Linux applications through container-like isolation, relying on bubblewrap namespaces, syscall filtering, and portal interfaces. In theory, each app should operate inside a strong sandbox, disconnected from the host system. But in reality, experience shows gaps, tiny cracks through which apps may escape with serious consequences. The Sandbox Promise… and the Reality Flatpak applications begin life in a highly-restricted environment: no network b...