The plugin 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).
1. Go to "Settings ยป Contact Form ยป Plugin Options" and in "Your Email", add the payload: 1" onmouseenter="alert(/XSS/) "
2. Then click on "Save Settings" and hove the mouse on the "Your Email" field to check the XSS popup.