In reply to Victor Poole.

The demo has an image (http://www.mashshare.net/wp-content/uploads/2014/03/mash-networks-demo.png) to click on to demo (that is how lightboxes work). As you can see, the image is just that, it is not a link to share something on Facebook.

Look at the source code (http://plugins.svn.wordpress.org/css3lightbox/trunk/) - I don't see any references to external sites in it. There is no malware there.

I don't see an options page in the code. In fact there is a comment:
/* redirect user to settings page after activation - comes later*/
and the function below it is commented out.