Bulletin Severity Rating:Important - This security update resolves a privately reported vulnerability in COM validation in Microsoft Office. The vulnerability could allow remote code execution if a user opens a specially crafted Excel, Word, Visio, Publisher, or PowerPoint file with an affected version of Microsoft Office. The vulnerability cannot be exploited automatically through e-mail. For an attack to be successful a user must open an attachment that is sent in an e-mail message.

Read more at: Microsoft Security Bulletins