phpBB 2.0.17 and earlier allows remote attackers to bypass protection mechanisms that deregister global variables by setting both a GET/POST/COOKIE (GPC) variable and a GLOBALS[] variable with the same name, which causes phpBB to unset the GLOBALS[] variable but not the GPC variable.
marc.info/?l=bugtraq&m=113081113317600&w=2
secunia.com/advisories/17366
secunia.com/advisories/18098
securityreason.com/securityalert/130
securitytracker.com/id?1015121
www.debian.org/security/2005/dsa-925
www.hardened-php.net/advisory_172005.75.html
www.osvdb.org/20386
www.securityfocus.com/bid/15243
exchange.xforce.ibmcloud.com/vulnerabilities/22914