PicoCTF St3g0 Writeup: Extracting Hidden Data with zsteg

St3g0 is a picoCTF 2022 forensics challenge where the flag is hidden inside a PNG image.

Analysis

For PNG steganography challenges, zsteg is a good first tool because it checks common bit-plane and channel hiding patterns.

zsteg pico.flag.png

Flag

The tool output reveals the hidden flag.

Key Takeaways

1. Start PNG steganography checks with lightweight tools such as zsteg.
2. Hidden data often lives in least significant bits or unusual color channels.
3. Forensics solves are fastest when you match the file type to the right inspection tool.