Mo Beigi

CTF: Hackvent 2019
Link to challenge: https://academy.hacking-lab.com
Date Completed: 14 December 2019

Challenge

HV19.H4 Hidden Four

Solution

During the Day 14 challenge HV19.14 Achtung das Flag, our final flag looks quite interesting:
HV19{s@@jSfx4gPcvtiwxPCagrtQ@,y^p-za-oPQ^a-z\x20\n^&&s[(.)(..)][\2\1]g;s%4(...)%"p$1t"%ee}

The hints in the __DATA__ segment point us in the right direction:

So we evaluate the string as Perl code like so:

This prints out the content of our hidden flag:
Squ4ring the Circle

Flag:  HV19{Squ4ring the Circle}