SQL injection vulnerability in the u2u_send_recp function in u2u.inc.php in XMB (aka extreme message board) 1.9.6 Alpha and earlier allows remote attackers to execute arbitrary SQL commands via the u2uid parameter to u2u.php, which is directly accessed from $_POST and bypasses the protection scheme.
https://www.exploit-db.com/exploits/2105
https://exchange.xforce.ibmcloud.com/vulnerabilities/28159
https://docs.xmbforum2.com/index.php?title=Security_Issue_History