source: http://www.securityfocus.com/bid/16850/info

MySQL is prone to a query-logging-bypass vulnerability. This issue is due to a discrepancy between the handling of NULL bytes in the 'mysql_real_query()' function and in the query-logging functionality.

This issue allows attackers to bypass the query-logging functionality of the database so they can cause malicious SQL queries to be improperly logged. This may help them hide the traces of their malicious activity from administrators.

This issue affects MySQL version 5.0.18; other versions may also be affected.

PHP code designed to exploit this issue is provided:

mysql_connect(...);
mysql_query('/*'.chr(0).'*/ SELECT * FROM table');