It’s important to note that Codex was given access to the source code. In another comment thread that is currently on the front page (https://news.ycombinator.com/item?id=47780456), the opinion is repeatedly voiced that being closed source doesn’t provide a material benefit in defending against vulnerabilities being discovered and exploited using AI. So it would be interesting to see how Codex would fare here without access to the source code.
There are two levels below having the source. One is having the binary of the firmware, which could be decompiled by the AI and understood. And then the worst-case is what I'm dealing with currently, which is where there is no access to the firmware binary and the firmware is stored on the PCB in such a way to prevent sticking a chip clip on it and forcibly extracting it, so you're totally blind. (Just as you would be with a completely remote attempt)