The Custom Content Shortcode WordPress plugin through 4.0.2 does not validate one of its shortcode attribute, which could allow users with a contributor role and above to include arbitrary files via a traversal attack. This could also allow them to read non PHP files and retrieve their content. RCE could also be achieved if the attacker manage to upload a malicious image containing PHP code, and then include it via the affected attribute, on a default WP install, authors could easily achieve that given that they have the upload_file capability.
The Custom Content Shortcode WordPress plugin through 4.0.2 does not validate and escape some of its shortcode attributes before outputting them back in a page/post where the shortcode is embed, which could allow users with the contributor role and above to perform Stored Cross-Site Scripting attacks