The events-calendar WordPress plugin through 1.0.4 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/707d4b5b-8efe-4010-ba7d-80538545a2d5/