phpBB 2.0.20 does not properly verify user-specified input variables used as limits to SQL queries, which allows remote attackers to obtain sensitive information via a negative LIMIT specification, as demonstrated by the start parameter to memberlist.php, which reveals the SQL query in the resulting error message.
https://exchange.xforce.ibmcloud.com/vulnerabilities/26306
http://securityreason.com/securityalert/837
http://marc.info/?l=full-disclosure&m=114685931319903&w=2