MyBB (MyBulletinBoard) 1.1.0 does not set the constant KILL_GLOBAL variable in (1) global.php and (2) inc/init.php, which allows remote attackers to initialize arbitrary variables that are processed by an @extract command, which could then be leveraged to conduct cross-site scripting (XSS) or SQL injection attacks.
https://exchange.xforce.ibmcloud.com/vulnerabilities/25865
http://www.vupen.com/english/advisories/2006/1381
http://www.securityfocus.com/archive/1/431061/30/5580/threaded
http://secunia.com/advisories/19668
http://myimei.com/security/2006-04-14/mybb110globalphpparameterextracting.html