It uses functions like CONCAT and GROUP BY to intentionally trigger a duplicate-key error. The database's error message will then "leak" the information hidden inside the query (in this case, the results of the SELECT 1 or version info) back to the attacker's screen.
If you are a developer, you can stop these attacks using three main methods: It uses functions like CONCAT and GROUP BY
Only allow the types of characters you expect. If a user is searching for a "Keyword," they probably don't need to use parentheses or semicolons. If a user is searching for a "Keyword,"
These are hexadecimal representations of characters (like 'qbqvq') used as delimiters so the attacker can easily spot their "stolen" data in the middle of a messy error message. Why is it dangerous? like usernames, hashed passwords, or emails
like usernames, hashed passwords, or emails. How to Prevent It
This is the gold standard. Instead of building a query string with user input, you use placeholders ( ? ). The database treats the input strictly as data, never as executable code.
Ensure your database user account only has the permissions it absolutely needs. For example, a "read-only" web user shouldn't be allowed to access INFORMATION_SCHEMA .