The WP Post Popup WordPress plugin through 3.7.3 does not sanitise and escape some of its inputs, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup)
https://wpscan.com/vulnerability/bb8e9f06-477b-4da3-b5a6-4f06084ecd57