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EnglishWhat Is a CTF Writeup and What Should It Include?
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A CTF writeup is a structured account of how someone solved a Capture The Flag challenge: the problem, the reasoning, the exact steps and tools used, and the flag. Teams and individual players publish them to document their work, and readers use them to learn techniques they can apply to different challenges. They're most useful when you read them to understand the method, not to copy a final answer.
Who writes CTF writeups, and why
Writeups come from competitors at every level, from beginners recording their first solved challenge to experienced players documenting a novel exploit. georgeom.net is one example: a cybersecurity research and competition blog by George Omnet that, in the author's own description, "mostly covers bug bounty and CTF write-ups to document my work over time." That framing is typical — the primary motive is a personal record, with teaching as a side effect.
Common reasons to write one:
- Retention. Explaining a solution forces you to understand why it worked, not just that it did.
- Portfolio. A public writeup demonstrates practical skill to employers and peers.
- Community. Others hit the same wall and search for the challenge name.
The typical structure of a writeup
Most writeups follow a loose version of this order. The best ones make the reasoning visible, not just the commands.
| Section | What it contains |
|---|---|
| Challenge info | Name, category, point value, event, and any provided files or URL |
| Recon / initial analysis | What you observed first: source code, file type, network traffic, hints |
| Approach | The hypothesis or vulnerability class you suspected, and why |
| Exploitation steps | The actual commands, payloads, or scripts, in order |
| Flag | The captured flag, often partially masked to avoid spoiling the challenge |
| Tools used | Burp Suite, Ghidra, CyberChef, pwntools, and so on |
| Lessons learned | The takeaway, dead ends, and what you'd do differently |
Not every writeup needs every section. A short forensics challenge might need only a few lines; a multi-stage pwn challenge may run for pages.
How to read a writeup so you actually learn
The trap is scrolling to the flag and closing the tab. To get value:
- Read the challenge description first and stop. Form your own initial hypothesis before reading the author's.
- Predict the next step. At each stage, ask what you would try. When the author does something different, that gap is the lesson.
- Reproduce it yourself. Rebuild the challenge locally if files are provided, and run the same commands to see the output.
- Note the trigger, not the payload. The reusable knowledge is why the vulnerability existed, not the specific string that exploited it.
- Check the dead ends. Good writeups mention what didn't work — that's often more instructive than the successful path.
How writeups differ by challenge category
The structure stays similar, but the emphasis shifts:
- Web: request/response pairs, payloads, and the vulnerable code path. Screenshots of Burp Suite traffic are common.
- Crypto: the mathematical weakness, any scripts written to exploit it, and the reasoning behind the attack.
- Forensics: the artifacts examined, the tools used to carve or decode them, and the chain of evidence.
- Reverse engineering: decompiler output, annotated functions, and the logic recovered from the binary.
- Pwn / binary exploitation: the memory corruption, offset calculations, and the final exploit script.
- OSINT and misc: the search trail, sources consulted, and how scattered clues were connected.
What separates a good writeup from a bad one
A strong writeup is reproducible: a reader with the same starting files could follow it to the same flag. That means including exact commands, tool versions where they matter, and the reasoning at each fork. A weak writeup jumps from "I looked at the file" to "and then I got the flag," skipping the part the reader actually needs.
If you're writing your first one, a useful test is to hand it to someone who hasn't solved the challenge and see whether they can follow it without asking questions.