Advisory: Office 2000 Scripting

                        @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 [[email protected]]
        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://www3.l0pht.com/~dildog/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.

[email protected]
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L-ZERO-P-H-T