Select Null,null,null,null-- Uizf — {keyword} Union All

: This is likely a random string used as a unique identifier or "signature" to help the attacker find their specific test result in a large log file or report. Purpose of Such a Payload Attackers use this technique to:

: In some cases, these injections can be used to log in without a valid password. {KEYWORD} UNION ALL SELECT NULL,NULL,NULL,NULL-- Uizf

If you found this in a "complete report" (such as a security scan or a web server log), it indicates that an automated tool or a manual actor has the system. : This is likely a random string used