The WP Show Posts WordPress plugin before 1.1.4 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/3ef4783b-4e4a-4691-b858-a7fa8dada4ec