The Post SMTP plugin for WordPress is vulnerable to unauthorized modification of data due to a missing capability check on the handle_office365_oauth_redirect() function in all versions up to, and including, 3.8.0. This is due to the function being hooked to admin_init without any current_user_can() check or nonce verification. This makes it possible for authenticated attackers, with Subscriber-level access and above, to overwrite the sites Office 365 OAuth mail configuration (access token, refresh token, and user email) via a crafted URL. The configuration option is used during wizard setup of Microsoft365 SMTP, only available in the Pro option of the plugin. This could cause an Administrator to believe an attacker-controlled Azure app is their own, and lead them to connect the plugin to the attackers account during configuration after upgrading to Pro.
Weakness
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
Potential Mitigations
- Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries.
- Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
- For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
- For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.
- One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.
Related Attack Patterns
References
- https://plugins.trac.wordpress.org/browser/post-smtp/trunk/Postman/Wizard/NewWizard.php#L104
- https://plugins.trac.wordpress.org/browser/post-smtp/trunk/Postman/Wizard/NewWizard.php#L2109
- https://plugins.trac.wordpress.org/changeset/3484515/
- https://www.wordfence.com/threat-intel/vulnerabilities/id/323436b5-fbfe-4923-8b08-93c1fcabc016?source=cve