@Stake Inc.
                        L0pht Research Labs
   
                  www.atstake.com     www.L0pht.com


                          Security Advisory
           

            Advisory Name: Microsoft Office 2000 UA Control Scripting
             Release Date: 5-12-2000
              Application: Microsoft Office 2000
                 Platform: Windows 95/98, NT 4.0 and 2000
                 Severity: Malicious active content can execute regardless of
                           macro virus protection settings.
                   Author: DilDog [dildog@atstake.com]                       
            Vendor Status: Vendor contacted, official patch available
                      Web: http://www.L0pht.com/advisories.html

Overview: 

        Microsoft Office 2000 ships with an ActiveX control named "Microsoft Office
UA Control". It is installed by default and is categorized as being "safe for scripting".
The control is undocumented, and its interfaces are presumably used to script "Show Me"
demonstrations for Office 2000 help and 'office assistant' functionality. Analysis of the
control's interface reveals functionality to script almost any action in Office 2000
that the user could perform from the keyboard, including, but not limited to, lowering
the macro security settings to low. This action can be scripted from any HTML page viewed
with active scripting enabled, including both Internet Explorer and Outlook e-mail in
their default configurations.

Detailed Description:

        The Microsoft Office UA control exports a powerful interface for automating
commands withing the Office 2000 environment. The problem lies in the fact that the 
control should -not- be marked safe for scripting. The capabilities of this control
are such that scripting it via remote HTML and email sources makes it extremely dangerous.
A demonstration of the vulnerabilites associated with this control is provided below.

        The vulnerability demonstration performs the following actions:

1. Start instance of Microsoft Word by pointing a table frame to a 
   word document URL with no macros or active content.
2. Programatically create UA control
3. Attach UA control to first instance of Microsoft Word
4. Make Word the active application
5. Show the Tools/Macro/Security dialog 
6. Click on the 'LOW' security radio button
7. Click on the 'OK' button to confirm the change
8. Proceed to re-point a table frame to a word document URL with a macro, which
   runs without prompting.

The fact that this control exists and is installed in this particular fashion would
permit the construction of a worm of unparalleled devastation, as it would be able to
turn off macro virus protection and 'script' it's way to all of the people in your
address book.


Temporary Solution:

Disable Active Scripting in all Office 2000 applications, and in Internet Explorer.
It is no longer sufficient to turn on macro virus protection, as this vulnerability
allow those settings to be circumvented.

Vendor Response And Official Patch:

"Wanted to let you know that the patch is now live at
http://officeupdate.microsoft.com/info/ocx.htm, and the security bulletin is live at
http://www.microsoft.com/technet/security/bulletin/ms00-034.asp."


Proof-of-Concept Code:

A demonstration of this vulnerability is available at:

http://www.l0pht.com/advisories/ouahack/index.html

This demonstration will set your Word 2000 macro security settings to 'LOW'. An
option will be presented to set it back to 'HIGH' or 'MEDIUM'.

The demonstration code is intentionally written to be harmless, but a worst case 
scenario could easily involve more malicious code to perform such actions as file 
modification, propagating worms and virii, or providing external access to internal 
network resources.


dildog@atstake.com 
[ For more advisories check out http://www.l0pht.com/advisories.html ]
                                           L-ZERO-P-H-T