The Sitekit plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'sitekit_iframe' shortcode in versions up to, and including, 1.4 due to insufficient input sanitization and output escaping. 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://plugins.trac.wordpress.org/changeset/2970788/sitekit
https://plugins.trac.wordpress.org/browser/sitekit/trunk/inc/sitekit-shortcode-iframe.php#L3