There's a new paper/advisory at: http://bindshell.net/papers/ftppasv Here's a quick summary: A common implementation flaw in FTP clients allows FTP servers to cause clients to connect to other hosts. This seemly small vulnerability has some interesting consequences for web browser security (namely in Firefox, Opera and Konqueror). This paper discusses the FTP client flaw in detail and demonstrates how it can be used to attack web browsers. Proof of concept code is presented that extends existing JavaScript port-scanning techniques to scan any TCP port from Firefox (even though it now implements "port banning" restrictions). Because of the way the same-origin policy is applied it is also possible to perform banner-grabbing scans against arbitrary hosts. Finally, for services that don't return a banner an alternative fingerprinting technique is demonstrated which measures the time it takes servers to close inactive TCP connections.
