Disobey 2020 - CTF - Steganography - Hacker wallpaper Writeup
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File seemed corrupted, so Binwalked the hacker_wp.png:

binwalk hacker-wp.png

DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
64            0x40            Zlib compressed data, best compression
4323          0x10E3          Zlib compressed data, default compression
4846          0x12EE          Zlib compressed data, best compression

Extracted the content with:

binwalk --dd=".*" hacker_wp.png

Then examined the outcome with:

file *
10E3:                    ColorSync color profile 4.3, type lcms, RGB/XYZ-mntr device by lcms, 672 bytes, 9-9-2019 19:41:52 'GIMP built-in sRGBlc'
10E3.zlib:               zlib compressed data
12EE:                    empty
12EE-0:                  zlib compressed data
40:                      ASCII text
40.zlib:                 zlib compressed data

The textfile "40" seems to contain hex, so translated hex to text with CyberChef. The output had some point towards
jpg and then a lot of mangled content. So wrote the output to file instead. Then examined the output with binwalk:

binwalk file.dat 

DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
8             0x8             TIFF image data, little-endian offset of first image directory: 8
448           0x1C0           JPEG image data, JFIF standard 1.01

Extracted the content again with:

binwalk --dd=".*" file.dat

Then opened the 1C0 (JPEG) with Pinta and found the flag in the image:

BCTF{f1xed_jpg_0pens_again}