The string you provided is a designed to discover the number of columns in a database table. Breakdown of the Payload
: This part attempts to break out of the existing SQL query structure. The closing parenthesis ) is used to "close" a likely function or subquery in the application's original code. {KEYWORD}) UNION ALL SELECT NULL,NULL,NULL,NULL,NULL-- ZkhD
For more in-depth technical guides, you can visit the Web Security Academy or community forums like Medium . The string you provided is a designed to
: This is a comment indicator that tells the database to ignore the rest of the original query that follows. For more in-depth technical guides, you can visit
: This is likely a random string or a "signature" used by a vulnerability scanner (like Burp Suite or sqlmap) to track if the payload was successfully reflected in the application's response.