IIS 5.0 cross site scripting vulnerability - using .htw

Systems affected:
IIS 5.0/Windows 2000. Exploited with browser (IE,NC) but the problem is in the web server.

Risk: Medium
Date: 28 October 2000

Legal Notice:
This Advisory is Copyright (c) 2000 Georgi Guninski. You may distribute it unmodified. You may not modify it and distribute it or distribute parts of it without the author's written permission.

Disclaimer:
The opinions expressed in this advisory and program are my own and not of any company.
The usual standard disclaimer applies, especially the fact that Georgi Guninski
is not liable for any damages caused by direct or  indirect use of the information or functionality provided by this advisory or program.
Georgi Guninski, bears no responsibility for content or misuse of this advisory or program or any derivatives thereof.

Description:

Using specially designed URLs, IIS 5.0 may return user specified content to the browser.
This poses great security risk, especially if the browser is JavaScript enabled and the problem is greater in IE.
By clicking on links, just visiting hostile web pages or opening HTML email the target IIS sever may return user defined malicous active content.
This is a bug in IIS 5.0, but it affects end users and is exploited with a browser.
A typical exploit scenario is stealing cookies which may contain sensitive information.
 

Details:
The following URL:
----
http://iis5server/null.htw?CiWebHitsFile=/default.htm&CiRestriction="<SCRIPT>alert(document.domain)</SCRIPT>"
----
executes in the browser javascript provided by "iis5server" but defined by a (malicous) user.
The URL may be used in a link or a script.
If /default.htm does not exist another document must be specified.
 

Workaround:
Remove the .htw extension from application mappings.

Vendor status:
Microsoft was notified on 24 October.