parseflag.py

#!/usr/bin/env python

# 0B E5
# 4D E2
quack = b""
with open('newflag', 'rb') as f:
    while True:
        oldpos = f.tell()
        byte = f.read(1)
        newpos = f.tell()
        if oldpos == newpos:
            break
        if byte == b'\x0B' or byte == b'\x4D':
            byte = f.read(1)
            if byte == b'\xE5' or byte == b'\xE2':
                byte = f.read(1)
                quack += byte

with open('quack.bin', 'wb') as f:
    f.write(quack)