The WP Secure Maintenance WordPress plugin before 1.7 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/81725b17-532a-43e6-8ce5-fe50a2ed0819/