If a database is vulnerable, it will try to process this calculation. Because the resulting string (a mix of letters and the number 1) cannot be converted to a NUMERIC type, the database will throw an error message . An attacker looks for that specific error to confirm the database is open to manipulation.
The SELECT (CASE WHEN (5241=5241) THEN 1 ELSE 0 END) is a "true or false" test. Since 5241 always equals 5241, it returns 1 . If a database is vulnerable, it will try
The CHR() functions translate character codes into letters to bypass simple security filters. In this case, they spell out "qpxbq" and "qvpjq". If a database is vulnerable