The YaySMTP WordPress plugin before 2.2.2 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 when the unfiltered_html capability is disallowed (for example in multisite setup)
https://wpscan.com/vulnerability/941fadb6-0009-4751-b979-88e87ebb1e45