Brevo < 3.3.1 - Unauthenticated Authorization Bypass via Type Juggling

Description

The plugin is vulnerable to authorization bypass due to type juggling due to the use of loose comparison (==) instead of strict comparison (===) when validating the installation ID in the `/wp-json/mailin/v1/mailin_disconnect` REST API endpoint. This makes it possible for unauthenticated attackers to disconnect the Brevo integration, delete the API key, remove all subscription forms, and reset plugin settings by sending a boolean `true` value for the `id` parameter, which bypasses the authorization check through PHP type juggling.