# Jellyspotters

## Challenge

The leader of the Jellyspotters has hired you to paint them a poster for their convention, using this painting program. Also, the flag is in \~/flag.txt.

nc umbccd.io 4200

Author: nb

## Solution

B64 encoded pickle string is loaded.

![](/files/-M_EDHEdKcZ9JbLJsD0k)

Reference: <https://davidhamann.de/2020/04/05/exploiting-python-pickle/>

We can leverage the `__reduce__` method to call `os.system()` with `cat ~/flag.txt`.

![](/files/-M_EDLFIxeAmp5R2QVsQ)

Passing the b64 encoded string into the input, we get the flag.

![](/files/-M_EDMhpK_7ZD6vNW0JW)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://ctf.zeyu2001.com/2021/dawgctf-2021/jellyspotters.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.