: This is a comment character in MySQL. It tells the database to ignore the rest of the original SQL statement, ensuring the injected command doesn't cause a syntax error [1]. Purpose: Blind SQL Injection

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This technique is known as [3].

If the payload works, an attacker can replace SLEEP(5) with more complex queries (e.g., IF(SUBSTRING((SELECT password FROM users),1,1)='a', SLEEP(5), 0) ) to extract data character-by-character based on whether the server pauses [3]. Security Implications

Malicious use of SLEEP() can lead to Denial of Service (DoS) by overloading the database with connection requests [3]. How to Prevent This Attack

This confirms a high-severity vulnerability that could allow attackers to bypass authentication, read sensitive data, or modify database contents.

Ensure the database user account used by the web application has limited permissions.