The is one of the more formidable challenges in the Hacker101 CTF (Capture The Flag) platform, requiring a deep dive into both web exploitation and advanced cryptography. Rated with a hard difficulty level and containing four flags , this challenge serves as a practical lesson in how even "military-grade" 128-bit AES encryption can be bypassed if the implementation is flawed. The Core Vulnerability: Padding Oracle Attack
The attacker can retrieve the admin bot’s decrypted paste content, which contains the flag. hacker101 encrypted pastebin
: You need to craft a valid encrypted string that decrypts to a different command or ID (e.g., changing "id": "123" to "id": "1" ). Hacker101 Encrypted Pastebin The is one of the
If you are currently trying to solve it, here are the key concepts you'll need to master: Automation is Key The Goal : You need to craft a
: Once you understand the plaintext structure, you can manipulate the ciphertext to "flip" specific bits. Since AES-CBC links blocks together, changing one byte in a ciphertext block directly modifies the corresponding byte in the next decrypted block. This allows you to alter things like IDs or usernames within the application's logic. SQL Injection via Encryption
In some versions of this challenge, there’s a side-effect. The server returns different error messages for “invalid padding” vs. “decryption failed.” That’s enough to decrypt arbitrary pastes over time.
Set expiration to (never "Never"). Click "Create New Paste."