Microsoft Security Bulletin (MS99-043)

[aleph1 () UNDERGROUND ORG (Aleph One)]

The following is a Security  Bulletin from the Microsoft Product Security
Notification Service.

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Microsoft Security Bulletin (MS99-043)
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Patch Available for "Javascript Redirect" Vulnerability
Originally Posted: October 18, 1999
Re-released: November 17, 1999

Summary
=======
On October 18, 1999, Microsoft released the original version of this
bulletin, in order to advise  customers of a workaround for a vulnerability
in Microsoft(r) Internet Explorer. The  vulnerability could allow a
malicious web site operator to read files on the computer of a user  who
visited the site, under certain circumstances. Microsoft has completed a
patch that  completely eliminates the vulnerability, and has re-released
this bulletin in order to advise  customers of its availability.

Frequently asked questions regarding this vulnerability can be found
at http://www.microsoft.com/security/bulletins/MS99-043faq.asp.

Issue
=====
Client-local data that is displayed in the browser window can be made
available to the server by  using a redirect to a Javascript applet running
in the same window. This in effect bypasses  cross-domain security and makes
the data available to the applet, which could then send the data  to a
hostile server. This could allow a malicious web site operator to read the
contents of files  on visiting users' computers, if he or she knew the name
of the file and the folder in which it  resided. The vulnerability would not
allow the malicious user to list the contents of folders,  create, modify or
delete files, or to usurp any administrative control over the machine.

Affected Software Versions
==========================
 - Microsoft Internet Explorer 4.01 and 5.

Patch Availability
==================
 - http://www.microsoft.com/downloads
 - http://www.microsoft.com/msdownload/iebuild/jsredir/en/jsredir.htm

   NOTE: The IE 4.01 patch requires IE 4.01 SP2 in order to install.
   IE 4.01 SP 2 is available at
   http://www.microsoft.com/Windows/ie/download/windows.htm.

   NOTE: The patch will be available shortly via the WindowsUpdate
   site.  When this happens, we will modify this bulletin to provide
   additional information.

More Information
================
Please see the following references for more information related to this
issue.
 - Microsoft Security Bulletin MS99-043: Frequently Asked Questions,
   http://www.microsoft.com/security/bulletins/MS99-043faq.asp.
 - Microsoft Knowledge Base (KB) article Q244356,
   Update for "Javascript Redirect" Vulnerability in Internet
   Explorer 4.01,
   http://support.microsoft.com/support/kb/articles/q244/3/56.asp.
 - Microsoft Knowledge Base (KB) article Q244357,
   Update for "Javascript Redirect" Vulnerability in Internet
   Explorer 5,
   http://support.microsoft.com/support/kb/articles/q244/3/57.asp.
 - Microsoft Security Advisor web site,
   http://www.microsoft.com/security/default.asp.

   NOTE: It may take 24 hours from the original posting of this
   bulletin for the KB articles to be visible.

Obtaining Support on this Issue
===============================
This is a fully supported patch. Information on contacting Microsoft
Technical Support is available at
http://support.microsoft.com/support/contact/default.asp.

Revisions
=========
 - October 18, 1999: Bulletin Created.
 - November 17, 1999: Bulletin re-released to provide information
   on availability of patch.

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