The Blog-in-Blog plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'blog_in_blog' shortcode in versions up to, and including, 1.1.1 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers with editor-level and above permissions to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
https://plugins.trac.wordpress.org/browser/blog-in-blog/tags/1.1.1/blog-in-blog.php#L257