The Slick Sitemap plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's 'slick-sitemap' shortcode in all versions up to, and including, 2.0.0 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
https://wordpress.org/plugins/slick-sitemap/
https://plugins.trac.wordpress.org/browser/slick-sitemap/trunk/slick-sitemap.php#L95