The following is a Security Bulletin from the Microsoft Product Security
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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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