The FancyBox for WordPress plugin before 3.0.3 for WordPress does not properly restrict access, which allows remote attackers to conduct cross-site scripting (XSS) attacks via an mfbfw[*] parameter in an update action to wp-admin/admin-post.php, as demonstrated by the mfbfw[padding] parameter and exploited in the wild in February 2015.
https://wordpress.org/plugins/fancybox-for-wordpress/changelog/
https://plugins.trac.wordpress.org/changeset/1082625/
http://www.securityfocus.com/bid/72506
http://www.openwall.com/lists/oss-security/2015/02/05/10
http://blog.sucuri.net/2015/02/zero-day-in-the-fancybox-for-wordpress-plugin.html