Tlen.PL e-mail XSS vulnerability.

As written in:

::File: 060416_XSS_tlen_pl
::Date: 16 Feb 2006
::Author: Tomasz Koperski <koper@xxxxxxx>

Tlen.PL e-mail system is affected to cross-site scripting vulnerability, not validating HTML tags in e-mail message subject.

Tlen.PL is a popular Polish IM system provided by, which includes e-mail accounts, and e-mail client built into the
communicator software (under Windows it is actualy an instance of Internet Explorer, displaying webmail system).
Depending on the server 'assigned' to the account (varying probably by the date of registration), webmail client does
not validate e-mail subject for HTML tags, allowing attacker to inject script code.
The vulnerable server is accessed by default with IM client (by older accounts).
The vulnerable server does not provide webmail services through default web browser access
(using for ex.:,, yet it is still accessible under
and used inside IM client.
On the account tested (login: koper, served by,, registered over 5 years ago), the lenght of
subject displayed is 28 characters, which is the lenght an attacker can use to inject HTML.

An attacker could include some of this code inside the subject field of e-mail sent to the target account:

<iframe src="";

//(28 chars, no HTML ending bracket, still page is displayed inside <iframe>,
//giving an attacker the ability to include more code. Having shorter domain name allows an
//attacker to give valid <iframe> tag.


//Displays 2 chars alert window


None provided, Vendor contacted on 16 Feb 2006.

::6::Systems affected::
All Communicator versions, but not all accounts affected.
Servers checked to be vulnerable: [ ].
Servers checked NOT to be vulnerable: [ ].