Unknown File

We are given an unknown file file with no extension. As usual, let's file it to get more informations.


It seems it didn't recognize anything. Let's open the file with hexedit to see what it contains exactly.


We can see interesting words such as "IHDR", "sRGB" or "pHYs". We also recognize XMP metadata.

We are clearly in front of a PNG file. The issue is, the magic bytes seems corrupted. The magic bytes of PNG files is supposed to be 89 50 4E 47 0D 0A 1A 0A, but as you can see in the file, while the last 4 are correct, the first 4 are wrong. Let's fix them and save that patched version as flag.png.


We open the image, and there we go:


Flag: KCTF{Imag3_H3ad3r_M4nipul4t10N}