{keyword}) Union All | Select Null,null,null,null,null-- Zkhd

An attacker (or security researcher) would send this payload to an application to see if it returns an error or a successful response.

: 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. {KEYWORD}) UNION ALL SELECT NULL,NULL,NULL,NULL,NULL-- ZkhD

: The number of NULL values (5 in this case) does not match the number of columns in the original table. An attacker (or security researcher) would send this

The string you provided is a designed to discover the number of columns in a database table. Breakdown of the Payload {KEYWORD}) UNION ALL SELECT NULL,NULL,NULL,NULL,NULL-- ZkhD

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