source: https://www.securityfocus.com/bid/41521/info
Yappa (Yet Another PHP Photo Album) is prone to multiple remote command-execution vulnerabilities because it fails to properly validate user-supplied input.
An attacker can exploit these issues to execute arbitrary commands within the context of the vulnerable system.
Yappa 3.1.2 is vulnerable; other versions may also be affected.
http://www.example.com/yappa/yappa.php?thedir=[ command you ]
http://www.example.com/yappa/yappa.php?image=[ command you]
