Newsletter, SMTP, Email marketing and Subscribe forms by Sendinblue < 3.1.61 - Reflected XSS

The plugin does not sanitise and escape a parameter before outputting it back in the admin dashboard when the WPML plugin is also active and configured, leading to a Reflected Cross-Site Scripting which could be used against high privilege users such as admin

PoC

Make a logged in admin open a page containing the code below (the WPML, slug: sitepress-multilingual-cms, needs to be active and configured as well. The ID is a translated form ID)