: In MySQL, the hash symbol marks the rest of the line as a comment . This effectively deletes any remaining parts of the original developer's code (like a trailing WHERE clause or a closing quote) that would otherwise cause a syntax error. Why This Matters
To protect your application from this type of attack, you should avoid building queries using simple string concatenation. Instead, use: {KEYWORD}) UNION ALL SELECT NULL,NULL,NULL,NULL,NULL,NULL#
The string you provided is a specific used to test for vulnerabilities in a database. It is designed to trick a web application into running a second, unauthorized query and appending the results to the original one. Breakdown of the Payload : In MySQL, the hash symbol marks the