The Ninja Forms WordPress plugin before 3.10.1 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/2adaa55a-4a6d-40ca-ae19-fcb82420894a/