Parade_buster-final.7z

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

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 Parade_Buster-Final.7z

: To solve this, a script was used to loop through all 376 files, extract a specific block of bytes (typically 0x11 bytes) from each, and concatenate them. Final Result The file Parade_Buster-Final

: Standard extraction and concatenation of the junk files failed to yield a valid binary. CTFtime

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

: 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 :