Mautic versions before 3.3.4/4.0.0 are vulnerable to an inline JS XSS attack through the contact's first or last name and triggered when viewing a contact's details page then clicking on the action drop down and hovering over the Campaigns button. Contact first and last name can be populated from different sources such as UI, API, 3rd party syncing, forms, etc.
Credits
Reported by Hoang Nguyen https://github.com/MatisAct, Fixed by Rohit Pavaskar https://github.com/rohitp19
