What's interesting to me about this is that it targets Claude's specific tics. Anthropic has created model that reliably reaches for the same tools (yes, and phrases; `python -c` is a load-bearing tool for it). Everyone gets the same model, so by learning the model's behavioral patterns you can target it better.
This default-to-auto-mode and the misleading marketing is begging for a class action once damages accumulate. Especially considering the Auto Mode even can actively prevent the clean-up!
The point is that auto mode gives people a false sense of security that leads them to believe they don't need to run Claude in a proper sandbox. This same attack running in a sandbox (even in YOLO mode) would be comparatively harmless.
I don’t think it’s related to the auto mode at all. It would work perfectly in the manual mode. It does not even need Claude: just give a human a similar archive and hope they run some simple Python from the directory at least once. And make sure there are lots of files do they don’t notice a weird .py around
As discussed [here](https://lobste.rs/s/ktbweg/prompt_injection_claude_code_opus...), this is not prompt injection. The prompt was to summarize the website, and in the process of summarizing the website, Claude writes a decoding script that it runs in an insecure and exploitable way. At no point was the intent of the agent hijacked, this was just code. Which is potentially more interesting!
I would not really call this a prompt injection attack, since it doesn't really hijack the agent to become malicious (something the article does discuss later on). It's more a trojan that's aimed at tricking Claude specifically.
That's an interesting technique! I'd also like to point out that there's something odd with the page itself too, my phone got really hot while I was reading the page, and drained a significant amount of battery charge as well.
They only mention it in passing, but I think it's mainly just the default tool call (which isn't wget, it's a built-in thing in the harness) just throwing off Claude's habits a bit (and not always just downloading the file).
As a non Python dev this seems like very surprising behavior for a system library to be modified by just having a file with a specific name in the same folder.
You would get a similar thing in C and C++ with a system header in a library directory (maybe some compilers would warn on such a thing?). Most languages don't privilege their standard libraries in a way that would prevent this.
See, that's why you should run with --dangerously-skip-permissions
> I got attack success rates up to 80% using a small sample size.
Snake oil salesman misrepresents the data. Color me surprised! /s