TL;DR. Ransomware written in Python and compiled to PYC. Encrypts the file `flag.png` to `flag.enc` using AES-CBC. Cryptographic secrets are found in the ransomware; use them to decrypt the given encrypted flag file. Find the actual flag image embedded at the end of the decrypted flag image file.

Original writeup (https://nave1337.herokuapp.com/index.html#bbf2021_ransomware).