Many "nested zip" challenges use a pattern where the filename itself is the key.
If "11-20" implies a range, this file likely contains 12.7z , which contains 13.7z , all the way to 20.7z or flag.txt . 11-20.7z
While there isn't a single famous global CTF challenge exclusively named , this file naming convention is a hallmark of forensics and steganography challenges where players must navigate deeply nested archives or "Russian Doll" files. Many "nested zip" challenges use a pattern where
: Extract the hidden flag from a series of nested or obfuscated archives. Step 1: Initial Reconnaissance : Extract the hidden flag from a series
The first step is always to identify what you are dealing with. Using the file command in Linux or a hex editor like 010 Editor helps verify the file header. : file 11-20.7z
: If you see a string ending in = , it's likely Base64.
: Confirms it is a 7-Zip archive. If the header was missing or corrupted, you would need to manually fix the magic bytes ( 37 7A BC AF 27 1C ). Step 2: Password Extraction (The "Base64" Trick)