A security vulnerability has been found in Internet Explorer 6, 7 and 8. With this, a hacker can take the control of your computer by injecting some code.
Before something is made to fix it up, they recommend to be careful when you are on internet and to unactivate ActiveX execution. You can also upgrade your version to 9 or 10.
Here is the Microsoft Security Advisory.
The versions 9 and 10 are non-affected by this vulnerability.