Clean Login < 1.13.7 - 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

Note: 1. First, you need to check “Choose the role(s) in the registration form?” in Clean Login Settings. 2. The form and the exploit only work and appear if you are not logged in to the website. Exploit shortcode: [clean-login-register role=‘" onmouseover=“alert(1)” style=“display:block !important; background:red;”’]