Microsoft has confirmed a report that criminals are emailing maliciously crafted Word attachments to victims. While these attacks are not widespread, they are dangerous because the attacker could run unauthorised software on the victim's computer if the attachment is opened.
This is the second such Word attack to be confirmed by Microsoft in the past week. Last Tuesday, Microsoft warned of a similar Word flaw, saying that it was aware of "limited attacks attempting to use the vulnerability".
Over the past year, hackers have increasingly looked to Microsoft's Office suite as a source of new bugs. Attacks based on flaws in Excel and PowerPoint have been reported as well.
Exploits of this latest flaw appear to be even rarer than those based on last week's Word bug.
"The vulnerability is being exploited on a very, very limited and targeted basis," Microsoft said in its alert.
Neither problem is expected to be fixed in today's software patches, which will address flaws in Windows and Visual Studio.
This second bug affects Word 2000, 2002, 2003 and the Word Viewer 2003, which are all vulnerable to last week's bug as well. The most recent version of the software, Word 2007, which was released to business users in late November, is not affected, Microsoft said.