WP Meta SEO <= 4.5.3 - Missing Authorization in 'saveSitemapSettings'

The WP Meta SEO plugin for WordPress is vulnerable to unauthorized plugin settings update due to a missing capability check on the saveSitemapSettings function in versions up to, and including, 4.5.3. This makes it possible for authenticated attackers with subscriber-level access to change sitemap-related settings of the plugin. This vulnerability occurred as a result of the plugin relying on nonce checks as a means of access control, and that nonce being accessible to all authenticated users regardless of role.