My script printed a green [OK]. The setting it was checking was correct. Both of those things were true, and neither of them mattered, because the check that printed [OK] was incapable of printing anything else.
I want to walk through how that happened, because I wrote it, and because I think it is the most common way security tools fail.
What I was building
I am a cybersecurity student, and I was setting up a lab to study an AI agent framework that NVIDIA released this month. The framework can execute code written by a language model. Their own documentation is blunt about what that means: generated code might delete files, send private data somewhere it shouldn't go, or modify the environment it runs in. They tell you to run it inside a virtual machine, isolated from your real files.
So I built one. A virtual machine with no shared folders, no clipboard sharing between the VM and my computer, no drag and drop. Every channel between the sandbox and my actual hard drive, switched off.
