The GZSEO plugin for WordPress is vulnerable to authorization bypass leading to Stored Cross-Site Scripting in all versions up to, and including, 2.0.11. This is due to missing capability checks on multiple AJAX handlers combined with insufficient input sanitization and output escaping on the embed_code parameter. This makes it possible for authenticated attackers, with contributor level access and above, to inject arbitrary content into any post on the site that will execute whenever a user accesses an injected page.