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/79d0a139-0fb3-4a4b-ac33-80cbc6cb3831/