CVE-2019-19980 in Email Subscribers
Summary
by MITRE
The WordPress plugin, Email Subscribers & Newsletters, before 4.2.3 had a privilege bypass flaw that allowed authenticated users (Subscriber or greater access) to send test emails from the administrative dashboard on behalf of an administrator. This occurs because the plugin registers a wp_ajax function to send_test_email.
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Analysis
by VulDB Data Team • 03/17/2024
The vulnerability identified as CVE-2019-19980 resides within the Email Subscribers & Newsletters WordPress plugin, affecting versions prior to 4.2.3. This flaw represents a significant security oversight that undermines the principle of least privilege and proper access control mechanisms. The issue manifests through a privilege escalation vector that allows users with subscriber-level permissions or higher to exploit administrative functions through the plugin's AJAX interface. The vulnerability specifically targets the wp_ajax function registered for sending test emails, which should normally be restricted to administrators but instead permits broader access. This misconfiguration creates a pathway for unauthorized users to perform administrative actions through the plugin's interface.
The technical implementation of this vulnerability stems from inadequate capability checks within the plugin's AJAX handler. When an authenticated user accesses the administrative dashboard and attempts to send a test email through the plugin's interface, the system fails to validate whether the requesting user possesses sufficient privileges to execute this administrative function. This oversight creates a direct bypass of WordPress's built-in permission systems, allowing users with subscriber roles or greater access to impersonate administrators within the plugin's context. The vulnerability operates at the application layer and leverages the legitimate wp_ajax functionality that WordPress provides for handling asynchronous requests, making it particularly challenging to detect and mitigate through traditional network-based security measures.
The operational impact of this privilege bypass vulnerability extends beyond simple unauthorized access, potentially enabling more sophisticated attacks within the compromised environment. An attacker with subscriber-level access could leverage this vulnerability to send emails on behalf of the administrator, potentially leading to phishing campaigns, spam distribution, or social engineering attacks that appear to originate from trusted administrative sources. The implications are particularly concerning in environments where the plugin is used for legitimate email marketing campaigns, as this could result in unauthorized promotional activities or malicious content distribution. Additionally, this vulnerability could serve as a stepping stone for further exploitation, as it demonstrates a weakness in the plugin's access control implementation that might indicate similar issues elsewhere in the application.
Organizations should immediately update the Email Subscribers & Newsletters plugin to version 4.2.3 or later to remediate this vulnerability. Security teams should also conduct comprehensive audits of their WordPress installations to identify any other plugins that may be susceptible to similar privilege escalation issues. The vulnerability aligns with CWE-284, which describes improper access control, and could be categorized under ATT&CK technique T1078 for valid accounts and T1566 for social engineering through email. Administrators should implement additional monitoring of administrative functions within the WordPress dashboard, particularly around email-related activities, to detect potential exploitation attempts. The incident highlights the importance of proper input validation and capability checking in web applications, especially when implementing AJAX-based administrative functions that require elevated privileges.