The Strong Testimonials WordPress plugin before 3.0.3 does not validate and escape some of its shortcode attributes before outputting them back in the page, which could allow users with a role as low as contributor to perform Stored Cross-Site Scripting attacks which could be used against high privilege users such as admins.
https://wpscan.com/vulnerability/14b679f5-44a8-46d4-89dd-94eb647cb672