The Paid Membership Plugin, Ecommerce, User Registration Form, Login Form, User Profile & Restrict Content WordPress plugin before 4.15.15 does not sanitise and escape some of its Membership Plan 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/a1e5ad16-6240-4920-888a-36fbac22cc71/