The WP Mail SMTP plugin for WordPress is vulnerable to information exposure in all versions up to, and including, 4.0.1. This is due to plugin providing the SMTP password in the SMTP Password field when viewing the settings. This makes it possible for authenticated attackers, with administrative-level access and above, to view the SMTP password for the supplied server. Although this would not be useful for attackers in most cases, if an administrator account becomes compromised this could be useful information to an attacker in a limited environment.
The storage of passwords in a recoverable format makes them subject to password reuse attacks by malicious users. In fact, it should be noted that recoverable encrypted passwords provide no significant benefit over plaintext passwords since they are subject not only to reuse by malicious attackers but also by malicious insiders. If a system administrator can recover a password directly, or use a brute force search on the available information, the administrator can use the password on other accounts.