The Schedulicity WordPress plugin through 2.21 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.
https://wpscan.com/vulnerability/b1a7e8fc-ffcf-493b-9f2d-ffa5d2348b60