The vulnerability identified as CVE-2026-1051 affects the 'Newsletter – Send awesome emails from WordPress' plugin, widely used to manage email newsletters on WordPress sites. The root cause is a Cross-Site Request Forgery (CSRF) flaw stemming from missing or incorrect nonce validation in the hook_newsletter_action() function. Nonces in WordPress are security tokens designed to verify that a request originates from a legitimate source and user intent. Without proper nonce validation, attackers can craft malicious URLs or web pages that, when visited or clicked by an authenticated user, cause unintended actions—in this case, unsubscribing newsletter subscribers. The vulnerability does not require the attacker to be authenticated but does require that the victim user is logged into the WordPress site and interacts with the malicious content. The impact is limited to the integrity of newsletter subscriber lists, as attackers can remove subscribers without authorization. There is no direct impact on confidentiality or availability of the system. The CVSS 3.1 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), user interaction required (UI:R), unchanged scope (S:U), no confidentiality impact (C:N), low integrity impact (I:L), and no availability impact (A:N). No patches or exploits are currently reported, but the vulnerability is publicly disclosed and should be addressed promptly.

For European organizations, this vulnerability primarily threatens the integrity of newsletter subscriber data by enabling unauthorized unsubscriptions. This can disrupt marketing campaigns, reduce subscriber engagement, and potentially damage brand reputation. While it does not compromise sensitive data confidentiality or system availability, the manipulation of subscriber lists can lead to loss of customer trust and operational inefficiencies. Organizations relying heavily on email marketing through WordPress sites using this plugin are at risk of targeted attacks aiming to sabotage their communication channels. Additionally, repeated or large-scale exploitation could indirectly affect business continuity by degrading the effectiveness of outreach efforts. The requirement for user interaction and logged-in status limits the attack surface but does not eliminate risk, especially in environments with many authenticated users or administrators.

To mitigate this vulnerability, European organizations should immediately update the 'Newsletter – Send awesome emails from WordPress' plugin to a version that includes proper nonce validation once available. In the absence of an official patch, administrators can implement custom nonce checks in the hook_newsletter_action() function to validate requests. Additionally, organizations should educate users about the risks of clicking suspicious links while logged into administrative or user accounts on WordPress sites. Employing Web Application Firewalls (WAFs) with rules to detect and block CSRF attack patterns can provide an additional layer of defense. Restricting user roles and permissions to the minimum necessary reduces the number of users who can be tricked into executing harmful actions. Regularly auditing plugin usage and monitoring logs for unusual unsubscribe activity can help detect exploitation attempts early. Finally, consider implementing multi-factor authentication (MFA) for WordPress accounts to reduce the risk of session hijacking that could facilitate CSRF attacks.