The Featured Image from URL (FIFU) WordPress plugin before 4.0.1 does not validate, sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks when the unfiltered_html capability is disallowed (for example in multisite setup)
https://wpscan.com/vulnerability/4481731d-4dbf-4bfa-b4cc-64f10bb7e7bf