The # character (used in MySQL/MariaDB) comments out the rest of the legitimate query, preventing syntax errors from trailing code [3]. 3. Potential Risk An attacker successfully using this technique can:
Security Audit Report: SQL Injection Vulnerability Critical / High Priority Location: Query Parameter {KEYWORD} 1. Vulnerability Summary {KEYWORD}) UNION ALL SELECT NULL,NULL#
UNION ALL SELECT NULL,NULL is used to determine the number of columns in the original query's SELECT statement. If the page loads without an error, the attacker knows the original table has exactly two columns [2]. The # character (used in MySQL/MariaDB) comments out
Access sensitive information like user credentials, emails, or financial records. Vulnerability Summary UNION ALL SELECT NULL,NULL is used
Sanitize inputs to block special characters like ) , # , and -- .
Ensure the database user account has the minimum permissions necessary, preventing access to system-level tables [4].