[Full-disclosure] Ipswitch FTP XSS leads to FTP server compromise

VDA Labs Advisory:

Ipswitch FTP XSS leads to FTP server compromise. The Vendor has been
notified, and given the PoC.

Synopsis:

There is XSS vulnerability when the WS_FTP server logs client FTP
commands. All user commands are logged. When the FTP command is invalid
(error), special characters are converted to HTML chars (< = &lt;, > =
&gt;), and logged. However, when the FTP command is valid, there is no
sanity check. Thus, it is possible to inject HTML and Javascript into
the log file.

The WS_FTP administration interface (IIS web application written in ASP)
has a view log option. When logs are viewed, it is possible to steal
the administrator cookie, or even better, DIRECTLY create a new user (or
admin) account for FTP server.

We've created a little PoC that will create a new system administrator
account when the admin view logs. The PoC is simple and injects an
<iframe> that leads to another html file that creates the new account.

Discovered by:

John Harwold, VDA Labs, LLC

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