The Easy Forms for Mailchimp WordPress plugin before 6.8.9 does not sanitise and escape some of its from parameters, 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/d3a2af00-719c-4b86-8877-b1d68a589192