The Email Encoder WordPress plugin before 2.3.4 does not sanitise and escape some of its settings, 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/7aeb6891-e159-4ed8-b1a9-a551140c9fcc/