The plugin does not validate and escape some of its shortcode attributes before outputting them back in a page/post where the shortcode is embedded, which could allow users with the contributor role and above to perform Stored Cross-Site Scripting attacks
Insert the following shortcode in a post/page: [gs_envato theme='" onmouseover="alert(1)" style="background:red;width:100px;height:100px;"']
Hover over the red square showing, and the alert will trigger.