Microsoft Security Bulletin (MS99-043)

--------------------------------------



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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