Some wordpress plugins contain external links to other websites with advertising!
In particular, a plugin called "Flash Clock Widget" that can be downloaded right here does this.
Read more about it here: http://www.mansurovs.com/beware-of-wordpress-plugins
I would encourage everyone who has installed this plugin to either remove the bad code as shown in the above URL, or uninstall it from your website.
Moderators, please ban both the plugin and the plugin author and let the community know as soon as possible!