Strange myFxSearchImg:base64 code in wordpress posts

When writing and pasting text into a wordpress blog post, I found that some strange code like

<img style="border: medium none"
src="image/png;base64,iVBORw0KGgoAAAANS ......

was added automatically at the end of the post.
First thought was some trojan/virus. After looking deeper into it, I found it's only a Vista Aero(Firefox theme) error.

And that code is nothing but this image:




To fix this issue, either remove Vista Aero or update it to the latest version.