The Melhor Envio plugin for WordPress is vulnerable to Sensitive Information Exposure in all versions up to, and including, 2.15.9 via the 'run' function, which uses a hardcoded hash. This makes it possible for unauthenticated attackers to extract sensitive data including environment information, plugin tokens, shipping configurations, and limited vendor information.
https://plugins.trac.wordpress.org/browser/melhor-envio-cotacao/trunk/Services/TestService.php#L30
https://plugins.trac.wordpress.org/browser/melhor-envio-cotacao/trunk/Services/TestService.php#L20