Excellent so far, although I've always thought of the entire interactive userland as the shell -- not only CLI, but also GUI, as each wraps the kernel on sort of the same plane.
Congrats to Cloudflare on this write-up. It’s interesting to have actual figures and a breakdown on how Shellshock is being exploited in the wild. Kudos for explaining the vulnerability in simple terms that a non-CLI user should be able to understand.