{keyword}') Union All Select Null,null,null,null,null,null,null-- Xhdx [OFFICIAL]

: This is a SQL comment. It tells the database to ignore everything that follows it, which prevents any remaining original code from causing a syntax error.

In short, this is not a legitimate feature of a software product, but rather a used to see if a website is properly "sanitizing" the text that users type into search bars or forms. : This is a SQL comment

: This attempts to "break out" of the original SQL query. It provides a keyword, then uses a single quote and a closing parenthesis to trick the database into thinking the intended command has ended. : This attempts to "break out" of the original SQL query

: This is likely a unique "fingerprint" or tag used by security researchers or automated scanning tools to identify if the injected code was successfully executed in the results. : This is a SQL comment