Post-09.rar Apr 2026

Identify the archive's contents and retrieve the hidden flag or "secret" data. 1. Initial Identification

The flag is typically found inside a .txt file within the archive or hidden within an image's metadata (EXIF) if an image was the only content extracted. FLAG{...} or CTF{...}

The first step is to verify the file integrity and type to ensure it isn't a "polyglot" (a file that acts as two different formats at once). POST-09.rar

If the archive is password-protected and no hint was provided in the challenge description: Use rar2john POST-09.rar > hash.txt .

Generate a SHA-256 hash to ensure the file hasn't been corrupted during transit. Identify the archive's contents and retrieve the hidden

Look for unusual high-entropy data at the end of the file. 5. Conclusion & Flag

Ensure the header starts with 52 61 72 21 1A 07 (RAR 5.0) or 52 61 72 21 1A 07 00 (RAR 4.0). Look for unusual high-entropy data at the end of the file

If the file list is hidden, the are encrypted (RAR 5.0 standard). 3. Cracking & Extraction (If Encrypted)