Flag: HQX{543c40987f3de029de611d3649428016}

Approach (Step by Step)

  1. The line ‘Somewhere in that mess, a flag is hiding in plain sight.’ hints that the flag is surely in a plaintext, i.e., easy to visible / proper format within the file.
  2. So I just extracted the zip file and got an .opt file and when I used the strings command on it to get readable text, I found multiple HQX texts messed up, among them all I got to see the actual flag.
  3. Just to filter it out I used grep along strings with regex: 'HQX\{[^}]{6,}\}'
  4. This regex finds a proper string with at least length of 6 between {}, to filter out all HQX{} (empty flags), any number would be fine, I randomly choose 6.

Output:

┌──(himanshu@Kaaammui)-[~/Desktop/tcs/noise]-(13-12-2025 10:13:54)
└─$ strings a729Ea1b97.opt | grep -E 'HQX\{[^}]{6,}\}'
HQX{4.MHQX{}!
HQX{Xr[HQX{}
[HQX{=iHHQX{}
>$HQX{8"aHQX{}
HQX{543c40987f3de029de611d3649428016} HQX{
_HQX{HQX{HQX{}
HQX{oHQX{h}
}HQX{HQX{-b}
HQX{%coX#h}
┌──(himanshu@Kaaammui)-[~/Desktop/tcs/noise]-(13-12-2025 10:14:28)
└─$

(actual output was big, I just skipped some for better visibility)

  1. To filter it down perfectly to just the flag, since I know the flag format typically contains a 32-character hex string, I increased the length to 32:
┌──(himanshu@Kaaammui)-[~/Desktop/tcs/noise]-(13-12-2025 10:14:28)
└─$ strings a729Ea1b97.opt | grep -E 'HQX\{[^}]{32,}\}'
HQX{543c40987f3de029de611d3649428016} HQX{