CVE-2024-39657: Sender Plugin CSRF Vulnerability

CVE-2024-39657 Overview

CVE-2024-39657 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the Sender – Newsletter, SMS and Email Marketing Automation for WooCommerce plugin for WordPress. The flaw impacts all plugin versions up to and including 2.6.18. The vulnerability maps to [CWE-352] and stems from missing or improperly implemented anti-CSRF protections on privileged plugin actions. An attacker who tricks an authenticated administrator into visiting a crafted page can trigger unauthorized state-changing operations within the plugin.

Critical Impact
Successful exploitation allows attackers to perform administrative actions in the context of a logged-in WordPress admin, leading to high impact on confidentiality, integrity, and availability of the affected site.

Affected Products

Sender – Newsletter, SMS and Email Marketing Automation for WooCommerce plugin for WordPress
All versions from n/a through 2.6.18
WordPress sites running WooCommerce with the Sender.net integration installed

Discovery Timeline

2024-08-26 - CVE-2024-39657 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-39657

Vulnerability Analysis

The vulnerability is a Cross-Site Request Forgery (CSRF) issue in the Sender plugin. CSRF flaws occur when a web application accepts state-changing HTTP requests without verifying that the request originated from a legitimate, intentional user action. In this plugin, one or more privileged endpoints fail to validate an anti-CSRF nonce or equivalent token. An attacker exploits the trust the application places in an authenticated session, causing the victim's browser to submit a forged request. The network attack vector, low complexity, and lack of required privileges make this issue attractive to opportunistic attackers, though user interaction is required.

Root Cause

The root cause is the absence of proper request-origin validation on sensitive plugin actions. WordPress provides the wp_nonce_field() and check_admin_referer() primitives for this purpose. When these controls are missing or misapplied on handlers that modify plugin configuration or trigger administrative operations, any authenticated session can be abused across origins. See the Patchstack Vulnerability Advisory for the specific handler details.

Attack Vector

Exploitation requires an authenticated WordPress administrator to visit an attacker-controlled page or click a crafted link while logged in. The attacker's page issues a hidden HTTP request, typically via an auto-submitting HTML form or an image tag, targeting a vulnerable plugin endpoint on the victim's WordPress site. Because the browser automatically attaches the administrator's session cookies, the server processes the request as legitimate. The attacker cannot read the response directly, but they can alter plugin settings, inject content, or trigger further actions that damage integrity and availability.

No verified public proof-of-concept code is available for CVE-2024-39657. See the referenced advisory for technical details on the affected endpoints.

Detection Methods for CVE-2024-39657

Indicators of Compromise

Unexpected changes to Sender plugin settings, API keys, or connected Sender.net account configuration.
Administrative actions in WordPress audit logs that were not initiated by a known admin session.
HTTP POST requests to Sender plugin admin endpoints with Referer headers pointing to third-party or unknown domains.
New or modified newsletter, SMS, or automation campaigns created outside normal operational hours.

Detection Strategies

Inspect WordPress access logs for requests to plugin admin handlers that lack a valid same-origin Referer or that arrive without a preceding admin page load.
Enable a WordPress activity logging plugin to record configuration changes made by administrator accounts and correlate them with browser session activity.
Deploy a web application firewall (WAF) rule that inspects Referer and Origin headers on wp-admin POST requests targeting the Sender plugin path.

Monitoring Recommendations

Monitor outbound email and SMS volumes from Sender.net for anomalous spikes indicating abuse of a compromised plugin configuration.
Alert on modifications to WordPress options table entries related to the Sender plugin, particularly stored API tokens.
Track administrator login sessions and cross-reference them with configuration change events to identify forged request patterns.

How to Mitigate CVE-2024-39657

Immediate Actions Required

Update the Sender – Newsletter, SMS and Email Marketing Automation for WooCommerce plugin to a version later than 2.6.18 as soon as a fixed release is available from the vendor.
Audit recent changes to plugin settings and Sender.net API credentials, rotating any tokens that may have been exposed.
Require administrators to log out of WordPress before browsing untrusted sites, and restrict administrative access to dedicated browser profiles.

Patch Information

The Patchstack Vulnerability Advisory tracks the fixed version. Verify the installed plugin version through the WordPress admin plugins page and apply updates through the standard WordPress update workflow.

Workarounds

Deactivate the Sender plugin until an updated version is installed if the plugin is not business-critical.
Deploy a WAF rule that blocks cross-origin POST requests to /wp-admin/admin.php and /wp-admin/admin-ajax.php when the Origin header does not match the site domain.
Enforce two-factor authentication for all WordPress administrator accounts to reduce the impact of session abuse.
Restrict administrative access to specific source IP addresses at the web server or reverse proxy layer.

bash

# Example Apache configuration to block cross-origin POSTs to wp-admin
<LocationMatch "^/wp-admin/(admin|admin-ajax)\.php$">
    SetEnvIfNoCase Origin "^https?://(www\.)?example\.com" allow_origin
    <RequireAll>
        Require method GET HEAD
    </RequireAll>
    <RequireAny>
        Require method GET HEAD
        Require env allow_origin
    </RequireAny>
</LocationMatch>