• we’re given a .zip file containing a .jpg image.

• the file can’t be opened, but we’re lucky : we are given a hint.

BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB
BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB
BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB

Let’s try replacing the BBBBBBBBBB in the file binary data.

To do that, I’ve chosen to use python.

#!/usr/bin/env python3

with open('chall.jpg', 'rb') as img:                        # open the .jpg file in 'read binary' mode
  binary_data = img.read()                                  # read the data and save it into a variable

data = binary_data.replace(b'BBBBBBBBBB', b'')              # replace the 10-B's sequence with nothing.

with open('ihopethisworks.jpg', 'wb') as img:               # open (and create, in this case) a new .jpg file
  img.write(data)                                           # write the resulted data into this file.

We’re able to open this image and obtain the flag.

FLAG: TFCCTF{the_{REDACTED}w4y}