The SendPress Newsletters WordPress plugin through 1.23.11.6 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/2772c921-d977-4150-b207-ae5ba5e2a6db/