Parade_buster-final.7z Online

The file Parade_Buster-Final.7z was the concluding challenge in the series from TastelessCTF 2020 . This write-up details the process of identifying a hidden PNG file embedded across hundreds of separate archives. Challenge Overview

: Standard extraction and concatenation of the junk files failed to yield a valid binary. Parade_Buster-Final.7z

The PNG file was striped and hidden in the trailing bytes of the 7z archives, just before the footer. The file Parade_Buster-Final

: Opening the first archive ( part2_0.7z ) in a hex editor revealed a PNG header ( 89 50 4E 47 ) and an IHDR chunk buried within the file structure itself, rather than in the extracted contents. The Pattern : The PNG file was striped and hidden in

Concatenating these extracted bytes from all files produced a final, valid image file named , which contained the flag for the challenge. CTFtime.org / TastelessCTF 2020 / 7/12 / Writeup

The offset for the hidden PNG data could be calculated by comparing the reported "Packed Size" from the 7z -slt l command with the actual file structure.