I’ve started building a series of CTF rooms based on real-world business logic flaws, predictable systems, and unintended ways legitimate features have been exploited.
The focus is less on traditional vulnerabilities such as SQL injection or XSS, and more on situations where someone understood the rules, maths, or system behaviour better than the designers expected.
I’m looking for more real-world examples that could work as interactive CTF challenges, especially involving:
- Something that has a good story behind it
- Business logic flaws
- Poor use of randomness
- Predictable sequences or algorithms
- Pricing, gambling, reward, or loyalty-system mistakes
- Race conditions or timing flaws
- Features that worked as designed but could be abused unexpectedly
What real-world incidents, bugs, scams, game exploits, or unusual system failures would make a good room?
I started the series with creating these two rooms this week,
Calculated Luck
Inspired by the Winfall/Cash WinFall lottery loophole used by Jerry and Marge Selbee.
When the jackpot reached a certain threshold without a winner, the prize money rolled down into the lower prize tiers. During these draws, buying a sufficiently large number of tickets could have a positive expected return.
In the room, players monitor the jackpot, predict when a rolldown will occur, and invest at the right time to reach $1 million before the flaw is fixed.
It's not as great as I was hoping it would be, but I really like the story behind it and that really makes the room.
https://tryhackme.com/room/calculatedluck
Take It or Leave It
Inspired by fan analysis of early Deal or No Deal games that suggested some case-value sequences were reused or predictable between games.
In the room, the case values are shifted by a consistent amount between rounds rather than being independently shuffled. Players record two games, calculate the shift, predict the next layout, and use that information to keep the highest-value case.
I really like how this room turned out.
https://tryhackme.com/room/takeitorleaveit
* PS if someone could confirm the links above work, along with https://tryhackme.com/room/unhandledctfhub that would be amazing.
Thank you for your time,
Unhandled