We covered a practical scenario on command injection using TryHackMe Epoch room.
Challenge Description
Be honest, you have always wanted an online tool that could help you convert UNIX dates and timestamps! Wait... it doesn't need to be online, you say? Are you telling me there is a command-line Linux program that can already do the same thing? Well, of course, we already knew that! Our website actually just passes your input right along to that command-line program!
Full writeup can be found here.
Video Walkthrough