[Alan_SP]

Idea is that image is on some other server, as explained in the first post:

Cookie stuffing is when a malicious user posts a hidden (clear) image in a post. Although you may never see the image it actually links to a location that will set a cookie on the browser of everyone viewing the post. In the cases of cookie stuffing this is almost always a cookie that contains their affiliate code for a site like Amazon or eBay. If anyone on your forum should go on to buy something from Amazon.com later in the day the spammer will get a credit from Amazon because your user has the spammer's cookie on their computer.

Attached images are on your server. Image doesn't have information, but location where image is does. That's the idea. So, only images on other servers may be a problem.