Just for fun, I signed up for the DEF CON CTF 2020 Qualifiers this weekend. I didn’t successfully solve any challenges besides the (deliberately easy) welcome challenges. But I spent a while working on “uploooadit,” a web challenge focusing on a Flask app. This post is a write-up of my unsuccessful attempts at solving the challenge. The Challenge The challenge links to a simple website and provides the source code, written in Python with the web framework Flask: