The Sitemap WordPress plugin before 4.4 does not validate and escape some of its shortcode attributes before outputting them back in the page, which could allow users with a role as low as contributor to perform Stored Cross-Site Scripting attacks which could be used against high privilege users such as admins.
Low privileged users can use the AJAX action 'cp_plugins_do_button_job_later_callback' in the Tree Sitemap WordPress plugin before 2.9, to install any plugin (including a specific version) from the WordPress repository, as well as activate arbitrary plugin from then blog, which helps attackers install vulnerable plugins and could lead to more critical vulnerabilities like RCE.