Print-O-Matic < 2.1.8 - Contributor+ Stored XSS via Shortcode

The plugin 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.

PoC

Exploit shortcode: [print-me class=“’ onmouseover=‘alert(1)’ style=‘background:red;’”]