The Strong Testimonials plugin for WordPress is vulnerable to arbitrary shortcode execution in all versions up to, and including, 3.2.16. This is due to the software allowing users to submit a testimonial in which a value is not properly validated or sanitized prior to being passed to a do_shortcode call. This makes it possible for unauthenticated attackers to execute arbitrary shortcodes if an administrator previews or publishes a crafted testimonial.
https://plugins.trac.wordpress.org/changeset/3381902/strong-testimonials