The Method method in WikkaWiki (Wikka Wiki) before 1.1.6.2 calls the strstr and strrpos functions with the wrong argument order, which allows remote attackers to bypass intended access restrictions and access arbitrary PHP files.
https://exchange.xforce.ibmcloud.com/vulnerabilities/27226
http://www.vupen.com/english/advisories/2006/2381
http://www.securityfocus.com/bid/18484