The Buy Me a Coffee WordPress plugin before 3.7 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/4dad1c0d-bcf9-4486-bd8e-387ac8e6c892