Multiple vulnerabilities have been reported in Microsoft Excel, which can be exploited by malicious people to compromise a user's system.

1) An error in the handling of macros can be exploited via a specially crafted Excel file to execute arbitrary code.

NOTE: According to Microsoft, this vulnerability is currently being actively exploited.

2) An error when processing data validation (DVAL) records can be exploited to corrupt memory via a specially crafted Excel file.

3) An error when importing files into Excel can be exploited via a specially crafted .slk file.

4) An error in the handling of style records can be exploited to corrupt memory via a specially crafted Excel file.

5) An error in the parsing of formulas can be exploited to corrupt memory via a specially crafted Excel file.

6) An error in the handling of rich text values can be exploited via a specially crafted Excel file.

7) An error in the handling of conditional formatting values can be exploited via a specially crafted Excel file.

Successful exploitation of the vulnerabilities may allow execution of arbitrary code.

Solution
Apply patches.
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Provided and/or discovered by
1) Discovered as a 0-day. The vendor also credits Matt Richard, VeriSign.
2) Greg MacManus, iDefense Labs.
3) The vendor credits Yoshiya Sasaki, JFE Systems.
4) The vendor credits Bing Liu, Fortinet.
5) Reported by an anonymous person via iDefense Labs.
6) Cody Pierce, TippingPoint DVLabs.
7) The vendor credits Moti Joseph and Dan Hubbard, Websense Security Labs.

Changelog
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Original Advisory
MS08-014 (KB949029):
http://www.microsoft.com/technet/security/Bulletin/MS08-014.mspx

Microsoft (KB947563):
http://www.microsoft.com/technet/security/advisory/947563.mspx

iDefense Labs:
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=671
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=672

TippingPoint DVLabs:
http://dvlabs.tippingpoint.com/advisory/TPTI-08-03

Other references
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Alternate/detailed remediation
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Deep Links
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