source: https://www.securityfocus.com/bid/55243/info
The Simple:Press Forum plugin is prone to a vulnerability that lets attackers upload arbitrary files. The issue occurs because the application fails to adequately sanitize user-supplied input.
An attacker may leverage this issue to upload arbitrary files to the affected computer; this can result in arbitrary code execution within the context of the vulnerable application.
http://www.example.com/wp/wp-content/plugins/simple-forum/forum/uploader/sf-uploader.php?id=4&folder=uploads/forum/petas