Bootstrap Shortcodes <= 3.4.0 - Contributor+ Stored XSS via Shortcode

The plugin 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

PoC

As a Contributor+ create a new post and add the following shortcode. [bs_well size=‘" onmouseover=“alert(1)” style=“background:red;width:100px;height:100px;”’] Save it to be reviewed. When an admin reviews the post and moves the mouse over the added code, the payload will be delivered.