CVE-2026-12757 in Email Subscribers & Newsletters Plugin
Summary
by MITRE • 09/07/2026
The The Email Subscribers & Newsletters – Email Marketing, Post Notifications & Newsletter Plugin for WordPress plugin for WordPress is vulnerable to arbitrary shortcode execution in all versions up to, and including, 5.9.27. This is due to the software allowing users to execute an action that does not properly validate a value before running do_shortcode. This makes it possible for unauthenticated attackers to execute arbitrary shortcodes.
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Analysis
by VulDB Data Team • 09/07/2026
The Email Subscribers & Newsletters plugin for WordPress, specifically in versions up through 5.9.27, contains a critical security flaw classified as an Arbitrary Shortcode Execution vulnerability. This issue stems from insufficient input validation within the plugin's handling of user-supplied data prior to processing it via the do_shortcode function. In typical WordPress environments, shortcodes are powerful tools that allow developers and users to embed dynamic content or execute specific functions using simple tags in posts or pages. However, when these shortcodes can be triggered by unauthenticated external actors without proper sanitization, they become a vector for unauthorized code execution. The vulnerability arises because the software fails to adequately verify the legitimacy of the input values before passing them into the shortcode processing engine, thereby bypassing intended access controls and allowing any visitor with internet connectivity to invoke internal plugin functionalities that should be restricted to authenticated administrators or specific contexts.
From a technical perspective, this flaw represents a classic case of improper neutralization of special elements used in an OS command (CWE-78) adapted for the WordPress shortcode ecosystem, often categorized under CWE-94 Improper Control of Generation of Code or CWE-200 Exposure of Sensitive Information if the executed shortcodes reveal data. The attacker can craft a malicious request that targets specific endpoints within the plugin where input is accepted but not rigorously checked against allowed patterns or user capabilities. By exploiting this gap, an unauthenticated adversary can inject arbitrary shortcode strings that interact with the WordPress core API or other installed plugins. This capability effectively grants the attacker a foothold in the application logic, potentially leading to Remote Code Execution (RCE) if specific shortcodes are configured to perform sensitive operations such as file manipulation, database queries, or system commands. The lack of authentication requirement significantly lowers the barrier for entry, making this vulnerability highly exploitable by automated scanning tools and opportunistic attackers alike.
The operational impact of this vulnerability is severe, potentially resulting in full website compromise. An attacker leveraging arbitrary shortcode execution can escalate privileges to gain administrative access, deface the website, steal sensitive customer data stored within the WordPress database, or install backdoors for persistent access. Furthermore, since email marketing plugins often handle subscriber lists and personal information, an exploit could lead to significant privacy violations and compliance failures under regulations such as GDPR or CCPA. The ability to execute arbitrary code also facilitates cross-site scripting (XSS) attacks if the output of the executed shortcodes is reflected in user-facing pages without proper encoding, thereby compromising the integrity and trustworthiness of the site for its visitors. This vulnerability undermines the fundamental security model of WordPress by allowing untrusted input to influence critical system behaviors.
To mitigate this risk, immediate action is required to update the Email Subscribers & Newsletters plugin to version 5.9.28 or later, where the developers have implemented stricter validation and sanitization routines for shortcode inputs. Administrators should also ensure that all other WordPress core components and plugins are up to date to prevent secondary exploitation vectors. Implementing a Web Application Firewall (WAF) can provide an additional layer of defense by filtering out malicious requests containing suspicious shortcode patterns before they reach the application logic. Additionally, enforcing strict access controls on administrative endpoints and disabling unnecessary plugin features that expose shortcodes publicly can reduce the attack surface. Regular security audits and penetration testing are recommended to identify similar input validation weaknesses across the entire WordPress installation, ensuring a robust defense-in-depth strategy against evolving threats aligned with MITRE ATT&CK techniques such as T1059 Command and Scripting Interpreter or T1190 Exploit Public-Facing Application.