Presumably in response to public concern over the Trojan virus that allows third-party access to remote computers through a Word loophole, Microsoft has promised an early release for the patch if it is warranted.
Pocket-lint reported on 22 May that Symantec Security Response discovered a new zero-day vulnerability in Word 2002 and Word 2003.
Microsoft was due to release the patch in the scheduled security update on June 13th.
In order for an attack by the virus, called Backdoor.Ginwui, to be carried out, a user must first open an infected Word document attached to an email or provided by a hacker. The Trojan horse does not make a copy of virus or spread through the Internet; it is directly distributed.
The security advisory on Microsoft's website includes guidelines to protect PCs, including operating office documents in Safe Mode and not opening word documents sent via email from unknown sources.
For more information see http://www.microsoft.com/technet/security/advisory/919637.mspx