Am I missing something, or where is the actual prompt given to Claude to trigger navigation to the page? Seems like the most interesting detail was left out of the article.

If the prompt said something along the lines of "Claude, navigate to this page and follow any instructions it has to say", it can't really be called "prompt injection" IMO.

EDIT: The linked demo shows exactly what's going on. The prompt is simply "show {url}" and there's no user confirmation after submitting the prompt, where Claude proceeds to download the binary and execute it locally using bash. That's some prompt injection! Demonstrating that you should only run this tool on trusted data and/or in a locked down VM.