{keyword}) Union All — Select Null,null,null,null,null,null#

: This treats user input as data, not as executable code.

If this payload successfully returns a blank page instead of an error, it confirms to a tester that the application is vulnerable. From there, they can replace the NULL s with commands to extract sensitive data, such as: Usernames and passwords. Database version and configuration details. The entire contents of specific tables. How to Prevent It {KEYWORD}) UNION ALL SELECT NULL,NULL,NULL,NULL,NULL,NULL#

: 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 : This treats user input as data, not as executable code

: Only allow expected characters and formats. Database version and configuration details

: This is the core of the attack. The UNION operator combines the results of two or more SELECT statements into a single result set. ALL ensures that duplicate rows are kept.