The Simple add pages or posts plugin for WordPress is vulnerable to Stored Cross-Site Scripting in all versions up to, and including, 2.0.0 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with administrator-level access, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This only affects multi-site installations and installations where unfiltered_html has been disabled.
https://wordpress.org/plugins/simple-add-pages-or-posts/#developers
https://plugins.trac.wordpress.org/browser/simple-add-pages-or-posts/tags/2.0.0/form.php