The User Role Editor plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 4.64.3. This is due to missing or incorrect nonce validation on the update_roles() function. This makes it possible for unauthenticated attackers to add or remove roles for arbitrary users, including escalating their privileges to administrator, via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.
The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.