# GET aHEAD

## Problem

> Find the flag being held on this server to get ahead of the competition <http://mercury.picoctf.net:47967/>

## Solution

1. Use Burp Suite to intercept the request of clicking the "Choose Blue" button.
2. Change the POST request to a HEAD request:

   ```
   HEAD /index.php HTTP/1.1
   Host: mercury.picoctf.net:47967
   Content-Length: 0
   Origin: http://mercury.picoctf.net:47967
   Connection: close
   ```
3. The returned HTML from the HEAD request in the browser will be empty, but in the HTTP history tab of Proxy in Burp Suite you can find the flag as a HTTP header in the response:

   ```
   HTTP/1.1 200 OK
   flag: picoCTF{r3j3ct_th3_du4l1ty_cca66bd3}
   Content-type: text/html; charset=UTF-8
   ```

### Flag

`picoCTF{r3j3ct_th3_du4l1ty_cca66bd3}`


---

# 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://picoctf2021.haydenhousen.com/web-exploitation/get-ahead.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.