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Microsoft Security Bulletin (MS99-060)
From: aleph1 () UNDERGROUND ORG (Aleph One)
Date: Wed, 22 Dec 1999 14:31:26 -0800
The following is a Security Bulletin from the Microsoft Product Security
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Microsoft Security Bulletin (MS99-060)
Patch Available for "HTML Mail Attachment" Vulnerability
Originally Posted: December 22, 1999
Microsoft has released a patch that addresses two issues:
- It eliminates a security vulnerability in the Microsoft(r)
Outlook Express mail client for Macintosh systems. The
vulnerability could allow attachments to HTML mails to be
automatically downloaded onto the user's computer.
- It provides replacements for several digital certificates
that are included in Internet Explorer for Macintosh, and
will expire on December 31, 1999.
Frequently asked questions regarding this patch can be found at
There are two issues here. The first is a security vulnerability found in
Outlook Express 5 for Macintosh. By design, when an HTML mail is received,
the mail content is downloaded onto the user's machine and processed.
However, attachments to the mail should not be downloaded unless the user
requests it. A flaw in Outlook Express 5 for Macintosh causes it to download
all content, including attachments. The vulnerability does not provide a way
for a malicious user to launch the downloaded attachments.
The second issue involves several digital certificates that are included in
Internet Explorer 4.5 for Macintosh. These certificates are due to expire on
December 31, 1999. The patch provides updated certificates, and also adds
support for X509 V3 certificates. There is no security vulnerability
associated with this issue; Microsoft is simply providing the replacement
certificates and X.509 V3 support as a community service.
It is important to note that both the security vulnerability and the
certificate expiration issue affect only Outlook Express and Internet
Explorer on the Macintosh; the Windows versions of these products are not
Affected Software Versions
- Microsoft Internet Explorer 4.5 for Macintosh
- Microsoft Outlook Express 5.0 for Macintosh (available as a
stand-alone product or bundled with Internet Explorer 5.0 for Macintosh)
NOTE: Additional security patches are available at the Microsoft Download
Please see the following references for more information related to this
- Frequently Asked Questions: Microsoft Security Bulletin MS99-060,
- Internet Explorer 4.5 Security Issue,
- Microsoft Knowledge Base (KB) article Q249082,
Outlook Express 5 for Macintosh Automatically downloads HTML
(Note: It may take 24 hours from the original posting of this bulletin
for this KB article to be visible.)
- Microsoft Security Advisor web site,
Obtaining Support on this Issue
This is a fully supported patch. Information on contacting Microsoft
Technical Support is available at
- December 22, 1999: Bulletin Created.
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- Microsoft Security Bulletin (MS99-060) Aleph One (Dec 22)