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

: Only allow expected characters and formats.

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#

: 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. : Only allow expected characters and formats

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 The UNION operator combines the results of two

: 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