The FTP protocol implementation in Opera 9.10 allows remote attackers to allows remote servers to force the client to connect to other servers, perform a proxied port scan, or obtain sensitive information by specifying an alternate server address in an FTP PASV response.
http://www.vupen.com/english/advisories/2007/1075
http://www.securitytracker.com/id?1017802
http://www.securityfocus.com/bid/23089
http://www.novell.com/linux/security/advisories/2007_28_opera.html
http://secunia.com/advisories/25027
http://bindshell.net/papers/ftppasv/ftp-client-pasv-manipulation.pdf