CVE-2026-73359 in Cookie Notice Plugin
Summary
by MITRE • 08/18/2026
Subscriber Cross Site Scripting (XSS) in WP Cookie Notice for GDPR, CCPA & ePrivacy Consent <= 4.3.9 versions.
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Analysis
by VulDB Data Team • 08/18/2026
The vulnerability identified as a Subscriber-level Cross-Site Scripting flaw within the WP Cookie Notice plugin affects versions up to and including 4.3.9. This security issue stems from insufficient input validation and sanitization mechanisms when handling user-supplied data related to cookie consent configurations. Specifically, the application fails to properly escape special characters in certain fields that are subsequently rendered on public-facing pages or within administrative interfaces without adequate encoding. This oversight allows an attacker with low-privilege accounts, such as subscribers, to inject malicious JavaScript code into web pages viewed by other users. The core technical flaw lies in the lack of robust output encoding for dynamic content derived from user inputs, which violates fundamental secure coding practices designed to prevent script injection attacks.
From a technical perspective, this vulnerability aligns with CWE-79, known as Improper Neutralization of Input During Web Page Generation, commonly referred to as Cross-Site Scripting (XSS). The attacker can exploit this weakness by crafting specific HTTP requests that contain malicious payloads within cookie consent settings or related form fields. When the application processes these inputs and renders them in a browser context without sanitizing script tags, event handlers, or other executable code vectors, the injected scripts execute in the victim's browser session. This execution occurs under the security context of the targeted website, granting the attacker significant capabilities within that domain. The vulnerability is particularly concerning because it does not require authentication at an administrative level, thereby expanding the pool of potential attackers to include any registered user with subscriber privileges on a WordPress site running this plugin version.
The operational impact of this vulnerability extends beyond simple script execution. Successful exploitation can lead to session hijacking, where the attacker steals cookies containing sensitive authentication tokens or session identifiers. This allows the adversary to impersonate legitimate users and gain unauthorized access to their accounts. Furthermore, the injected scripts can perform actions on behalf of the victim without their knowledge or consent, such as changing account settings, making purchases, or modifying content. In more severe scenarios, attackers may use this vector for phishing attacks by redirecting victims to malicious sites that mimic legitimate login pages, thereby harvesting credentials. The ability to execute arbitrary JavaScript also facilitates keylogging and data exfiltration from the victim's browser environment, compromising user privacy and potentially leading to broader organizational security breaches if administrative accounts are targeted through social engineering facilitated by this initial foothold.
This vulnerability maps directly to several techniques within the MITRE ATT&CK framework for web applications. It corresponds primarily to T1059, Command and Scripting Interpreter, specifically JavaScript execution in a browser context. Additionally, it relates to T1204, User Execution, as it relies on tricking users into visiting maliciously crafted pages or interacting with compromised content. The attack vector is classified under Initial Access via Browser Security Misconfiguration, highlighting the importance of proper input handling and output encoding in web application development. Understanding these mappings helps security teams prioritize remediation efforts based on established threat intelligence frameworks and industry best practices for mitigating client-side code injection risks.
To mitigate this vulnerability, site administrators should immediately update the WP Cookie Notice plugin to version 4.3.10 or later, where the input validation and output encoding issues have been addressed by the developers. Until an upgrade is feasible, implementing a Web Application Firewall (WAF) with rules specifically designed to detect and block XSS payloads can provide a layer of defense against exploitation attempts. Security teams should also enforce strict Content Security Policy headers that restrict the execution of inline scripts and limit sources from which JavaScript can be loaded. Regular security audits and code reviews focusing on input sanitization and output encoding are essential preventive measures. Additionally, applying the principle of least privilege ensures that even if an attacker gains subscriber-level access, their ability to cause widespread damage is limited by restricting what data they can modify or view within the application environment.