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:
Yesterday, this site went down for about four hours. Complaints started rolling in from my millions of ardent followers, spurring me into action. Join me as I deconstruct what went wrong, how I fixed it, and how I tried to prevent the problem from occurring again.
I erased all of my cronjobs by accident due to a simple typo.
When working with cron jobs, the command
crontab -e is used to edit your
crontab. This command is one letter off from
crontab -r, which erases your
cron jobs without any confirmation prompt. On a QWERTY keyboard,
r keys are adjacent, which makes it especially easy to type the
wrong one by accident. I accidentally typed the wrong thing, and
*poof*, my cronjobs disappeared.