If you are using this article for defensive training, here is how to prevent Challenge 5 from existing in your own code:
The fix is not just mysql_real_escape_string (which is outdated). Use:
In the , you are tasked with exploiting an injection vulnerability in a coupon code verification field to retrieve a hidden flag. Challenge Objective
The challenge’s filter is case-insensitive and strips or rejects the payload if any blacklisted word appears.
However, in MySQL, you can use PROCEDURE ANALYSE() to extract data, but that’s advanced.