Plugin does not sanitize and escape the URL field in the plugin settings, which could allow high-privilege users to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).
1. In the "Enter the URL: field, add the XSS payload `<img src=x onerror=alert(1)>` and save
2. Payload will be executed upon reload.