CVE-2026-1051 Overview
The Newsletter – Send awesome emails from WordPress plugin for WordPress contains a Cross-Site Request Forgery (CSRF) vulnerability in all versions up to, and including, 9.1.0. This security flaw exists due to missing or incorrect nonce validation on the hook_newsletter_action() function. The vulnerability enables unauthenticated attackers to unsubscribe newsletter subscribers via a forged request, provided they can trick a logged-in user into performing an action such as clicking on a malicious link.
Critical Impact
Unauthenticated attackers can manipulate newsletter subscriptions by exploiting the lack of CSRF protection, potentially disrupting email marketing campaigns and causing subscriber data integrity issues.
Affected Products
- Newsletter – Send awesome emails from WordPress plugin versions ≤ 9.1.0
- WordPress installations using the vulnerable Newsletter plugin
Discovery Timeline
- 2026-01-20 - CVE-2026-1051 published to NVD
- 2026-01-20 - Last updated in NVD database
Technical Details for CVE-2026-1051
Vulnerability Analysis
This vulnerability is classified as CWE-352 (Cross-Site Request Forgery). The core issue lies in the Newsletter plugin's failure to properly implement nonce verification within the hook_newsletter_action() function. Nonces in WordPress serve as security tokens to verify that requests originate from legitimate sources and protect against CSRF attacks. Without proper nonce validation, the plugin cannot distinguish between authentic user-initiated requests and malicious forged requests crafted by attackers.
The attack requires user interaction, meaning an attacker must convince an authenticated WordPress user (typically an administrator) to click a specially crafted link or visit a malicious page. When successful, the attacker can force the unsubscription of newsletter subscribers without authorization.
Root Cause
The root cause is the absence or improper implementation of WordPress nonce verification in the hook_newsletter_action() function located in the unsubscription handling code. The function processes subscription-related actions without first confirming that the request includes a valid security nonce, leaving the endpoint vulnerable to cross-origin requests.
Attack Vector
The attack is conducted over the network and requires user interaction. An attacker would craft a malicious HTML page or link containing a forged request targeting the vulnerable Newsletter plugin endpoint. When an authenticated WordPress user visits the attacker's page or clicks the malicious link, their browser automatically sends the forged request to the WordPress site, including the user's authentication cookies. Since the plugin fails to validate the request's authenticity through nonce checking, it processes the malicious unsubscription request as if it were legitimate.
The vulnerability specifically affects the unsubscription functionality, as documented in the WordPress Unsubscription Script. An attacker could exploit this to systematically unsubscribe users from mailing lists, causing disruption to email marketing operations.
Detection Methods for CVE-2026-1051
Indicators of Compromise
- Unexpected mass unsubscriptions from newsletter lists without user consent
- Audit logs showing unsubscription requests originating from suspicious referrer URLs
- Reports from subscribers stating they were unsubscribed without requesting it
- Unusual patterns in subscriber activity logs coinciding with external link clicks
Detection Strategies
- Monitor WordPress audit logs for bulk or rapid unsubscription events
- Implement web application firewall rules to detect CSRF attack patterns targeting Newsletter plugin endpoints
- Review HTTP referrer headers in web server logs for unsubscription requests originating from external domains
- Deploy SentinelOne Singularity XDR to detect and correlate suspicious web application activity patterns
Monitoring Recommendations
- Enable detailed logging for the Newsletter plugin's subscription management functions
- Configure alerts for abnormal unsubscription rates or volumes
- Implement real-time monitoring of WordPress administrative actions
- Review subscriber count changes and correlate with access logs for anomaly detection
How to Mitigate CVE-2026-1051
Immediate Actions Required
- Update the Newsletter – Send awesome emails from WordPress plugin to a version higher than 9.1.0 that includes the security fix
- Review recent subscriber unsubscription activity for signs of exploitation
- Educate WordPress administrators about the risks of clicking untrusted links while logged in
- Consider temporarily disabling the plugin if an immediate update is not possible
Patch Information
Users should update to the latest version of the Newsletter plugin that addresses this CSRF vulnerability. The fix involves implementing proper nonce validation on the hook_newsletter_action() function. Refer to the Wordfence Vulnerability Report for additional details on the security update.
Workarounds
- Implement a Web Application Firewall (WAF) rule to block suspicious requests to Newsletter plugin endpoints
- Restrict administrative access to trusted IP addresses only
- Use browser extensions that provide CSRF protection or isolate browsing sessions
- Advise administrators to use separate browser profiles for WordPress administration and general browsing
# WordPress CLI command to check Newsletter plugin version
wp plugin list --name=newsletter --fields=name,version,status
# Update Newsletter plugin to latest version
wp plugin update newsletter
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
