The Print-O-Matic WordPress plugin before 2.1.8 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/5d72ec1f-5379-4d8e-850c-afe8b41bb126