[Swordmaker]

This appears to be another Trojan... this time a Trojan Excel file. You cannot be damaged UNLESS you open the file.

• This vulnerability could not be exploited automatically through a Web-based attack scenario. An attacker would have to host a Web site that contains an Office file that is used to attempt to exploit this vulnerability. An attacker would have no way to force users to visit a malicious Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site.
MIcrosoft FAQ on the Excel security flaw.

[coconutt2000]

A trojan, in the wild, that attacks a Microsoft product causing it to crash is deemed a "flaw".

An unreleased example of a trojan on a Mac that still requires the user to give the trojan an admin username and password in order to do its dirty work is reason to panic.

[Swordmaker]

According to Microsoft, this flaw exists in the Mac OS X version of Excel as well as all current PC versions. However the flaw works by creating a buffer overflow.

The vulnerability is caused due to a boundary error in hlink.dll within the handling of Hyperlinks in e.g. Excel documents. This can be exploited to cause a stack-based buffer overflow by tricking a user into clicking a specially crafted Hyperlink in a malicious Excel document.
Secunia Excel Security Report

This is not as serious a flaw for Mac OS X users. Unlike Windows, OS X does not permit execution of any executable from the buffer... so the most it can do is to crash Excel on a Mac.

[Swordmaker]

Microsoft Excel buffer overflow flaw in a malicious Excel (including Mac version) spreadsheet can crash the application... and take over a PC (but not a Mac)... PING!

If you want on or off the Mac Ping List, Freepmail me.

[zeugma]

...It also recommends blocking such files when they arrive as e-mail attachments or changing PC settings so spreadsheets can't be opened from the Outlook e-mail client or the Web.

Is anyone else as peeved by this kind of stuff as I am? I've had serious issues trying to get data to people because of this idea of just blanket blocking of file types. It really pisses me off sometimes. A couple of times,  the only way I could get data to a vendor that I needed to have them look at was to ftp it to them.  

Microsoft malware is a plague.