CVE-2023-4599 in Email Encoder Plugin
Summary
by MITRE • 08/30/2023
The Email Encoder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'eeb_mailto' shortcode in versions up to, and including, 2.1.8 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers with contributor-level and above permissions to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. A partial patch was issued in version 2.1.8. The vulnerability was fully patched in 2.1.9.
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Analysis
by VulDB Data Team • 04/10/2026
The Email Encoder plugin for WordPress presents a critical stored cross-site scripting vulnerability identified as CVE-2023-4599 affecting versions up to and including 2.1.8. This vulnerability specifically targets the 'eeb_mailto' shortcode functionality where user-supplied attributes are inadequately sanitized and properly escaped during processing. The flaw exists within the plugin's handling of email encoding features that allow administrators to create clickable email links through shortcode implementation. Attackers exploiting this vulnerability can manipulate the plugin's shortcode processing logic to inject malicious javascript code that persists in the WordPress database and executes whenever affected pages are rendered. The vulnerability requires authentication with contributor-level permissions or higher, making it particularly concerning as it allows users with moderate privileges to compromise the entire WordPress installation through persistent script injection.
The technical root cause of this vulnerability stems from insufficient input validation and output escaping mechanisms within the plugin's shortcode implementation. When users with appropriate permissions create or modify posts containing the 'eeb_mailto' shortcode with malicious attributes, the plugin fails to properly sanitize these inputs before storing them in the database. This lack of proper sanitization creates a persistent XSS vector where malicious scripts are stored alongside legitimate content and executed in the context of other users who view the affected pages. The vulnerability manifests when the shortcode processes user-provided email addresses or other attributes without adequate escaping of special characters that could be interpreted as executable javascript code. This flaw aligns with CWE-79, which specifically addresses cross-site scripting vulnerabilities resulting from insufficient output escaping of user-controllable data.
The operational impact of this vulnerability extends beyond simple script execution as it provides attackers with the ability to perform various malicious activities within the compromised WordPress environment. Authenticated attackers can leverage this vulnerability to steal session cookies, redirect users to malicious websites, modify content displayed to other users, or even escalate their privileges within the WordPress installation. The stored nature of the vulnerability means that once exploited, the malicious scripts remain active until manually removed or until the plugin is updated to a patched version. This persistent threat can affect all users who access pages containing the compromised shortcode, making it particularly dangerous in multi-user environments where contributors and editors regularly create content. The vulnerability also enables attackers to perform reconnaissance activities by extracting user information, monitoring user activities, or conducting further exploitation attempts through the compromised execution environment.
The remediation process for this vulnerability requires immediate updating of the Email Encoder plugin to version 2.1.9 or later, which contains the complete patch addressing the input sanitization and output escaping deficiencies. Organizations should conduct thorough security audits of all WordPress installations to identify potentially compromised content and remove any malicious scripts that may have been injected prior to patching. System administrators should implement monitoring of plugin updates and maintain updated security practices including regular vulnerability scanning and access control reviews. The patch addresses the core issue by implementing proper input validation and output escaping mechanisms that prevent malicious attributes from being stored or executed in the shortcode processing pipeline. Security teams should also consider implementing web application firewalls and content security policies to add additional layers of protection against similar vulnerabilities in other plugins or themes. This vulnerability demonstrates the importance of proper input validation and output escaping in web applications, particularly those that process user-generated content through shortcode or template systems, and aligns with ATT&CK technique T1566.001 for social engineering through malicious content creation.