Eat the Cake! [rev, 641 solvers] TLDR; Simple re challenge written in C++, which checks every character of the input. Despite used language, it's easily reversible doing only static analysis. At the start of the challenge I was given one file called cake.exe. Quick file check revealed that it’s UPX packed binary. To unpack it I used standard tool available in kali repositories: ➜ upx -d cake.exe Ultimate Packer for eXecutables Copyright (C) 1996 - 2018 UPX 3.