The User Registration WordPress plugin before 3.0.4.2 does not sanitize 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/50ae7008-46f0-4f89-ae98-65dcabe4ef09