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

: This is a common reconnaissance technique. An attacker uses NULL values to determine the exact number of columns returned by the original query. If the number of NULL s doesn't match the original column count, the database will usually throw an error. By adding or removing NULL s, an attacker can find the correct structure.

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#

: Only allow expected characters and formats. : This is a common reconnaissance technique

: This treats user input as data, not as executable code. By adding or removing NULL s, an attacker

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

: 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.