There is some sort of vulnerability with this plugin. My site requires membership to post comments. However over the last week I have been getting hit with spam comments. These spam comments are coming in through add link to facebook's comment pingback. The comments look like they are being made on facebook, however there are no such comments on facebook. These same spammers have already been blacklisted from the site, and are not on facebook to my knowledge, yet they are able to spam my site with comments through this plugin now.