From ZDNet:
(emphasis added)
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The vulnerability is similar to previous so-called zero-day flaws that have hit Office applications in recent months. An attacker could rig a Word file in such a way that he would gain complete control over a vulnerable PC when the file is opened, Microsoft said in its advisory.
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The latest Office vulnerability affects Word 2000, Word 2002, Word 2003, Microsoft Word Viewer 2003, Word 2004 for Mac, Word 2004 version X for Mac, as well as Works 2004, 2005 and 2006, Microsoft said. As a way of protection, Microsoft suggests not opening or saving Word files from unknown sources or that arrive unexpectedly.
(emphasis added)