The Smart Maintenance Mode WordPress plugin before 1.5.2 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/1569ee00-56c3-4a1b-940e-e0256a748675/