The Meta-box GalleryMeta plugin for WordPress is vulnerable to Stored Cross-Site Scripting via admin settings in all versions up to, and including, 3.0.1 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with editor-level permissions and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This only affects multi-site installations and installations where unfiltered_html has been disabled.
https://plugins.trac.wordpress.org/browser/meta-box-gallerymeta/tags/3.0.1/gallerymetaboxes.php#L314
https://plugins.trac.wordpress.org/browser/meta-box-gallerymeta/tags/3.0.1/gallerymetaboxes.php#L119