TWiki 4.0.0, 4.0.1, and 4.0.2 allows remote attackers to gain Twiki administrator privileges via a TWiki.TWikiRegistration form with a modified action attribute that references the Sandbox web instead of the user web, which can then be used to associate the user's login name with the WikiName of a member of the TWikiAdminGroup.
https://exchange.xforce.ibmcloud.com/vulnerabilities/27336
http://www.vupen.com/english/advisories/2006/2415
http://www.securityfocus.com/bid/18506
http://twiki.org/cgi-bin/view/Codev/SecurityAlertTWiki4PrivilegeElevation
http://securitytracker.com/id?1016323
http://secunia.com/advisories/20596
http://archives.neohapsis.com/archives/vulnwatch/2006-q2/0032.html