Finones said that the code "reliably exploits this [Word] vulnerability."

Last month, Microsoft rated the RTF vulnerability as "critical" in Word 2007 and 2010, but as "important" in all other affected versions.

At the time, outside researchers had put their bets on the bug as a hacker choice because users running Office 2007 or 2010 could be attacked if all they did was preview a specially-crafted RTF document in the Outlook e-mail client.

"Once a [malformed] message hits the Outlook preview pane, remote code can be executed. You should patch this right away," Jason Miller, the data and security team manager for Shavlik Technologies, said on the day Microsoft released the patch.

Finones urged users who have not yet installed the November patch to do so as soon as possible.