Yet another 0-day vulnerability is being actively exploited. This one, discovered only a few days after the previous one, lets intruders install shell code and from there a whole slew of bad things can happen. Be sure you're protected!
Read our related news story, "IE Vulnerable to Remote Code Execution," and Microsoft's associated Security Advisory (linked in the news story) and take defensive measures. If you missed the previous report, issued on September 15, then be sure to read that one too.