# Chandi Bot 4

- 183 Points / 147 Solves

## Background

Can you beat the bot?


## Find the flag

In this challenge, we need 3 commands: ***`/balance` to check how many point we have, `/rps` to play "Rock Paper Scissors" to gain points, `/dad` to gain 1 point, `/buy-flag` to buy flag for 10000 points***

**First, let's check our balance:**


We got 0 point.

**Then, gain 1 point by using `/dad` command:**


**Next, use `/rps` to play "Rock Paper Scissors":**


Hmm... we can't wager 0 points...

I wonder can we go negative points:


Ohh!! We can! And we gain 1 point!!

**Let's use that logic vulnerbility to gain 9999999 points!!**
```
/rps choice:Rock wager:-9999999
```


Boom! We have 10000001 points!!

**Finally, we can use `/buy-flag` command to buy the flag!**


- **Flag: `RS{TWO_NEGATIVES_DO_MAKE_A_POSITIVE}`**

## Conclusion

What we've learned:

1. Exploiting Logic Vulnerability

Original writeup (https://siunam321.github.io/ctf/RITSEC-CTF-2023/Chandi-Bot/Chandi-Bot-1-6/#chandi-bot-4).