CVE-2015-4367 in Simple Subscription Module
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Simple Subscription module before 6.x-1.1 and 7.x-1.x before 7.x-1.1 for Drupal allows remote authenticated users with the "administer blocks" permission to inject arbitrary web script or HTML via vectors related to block content.
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Analysis
by VulDB Data Team • 04/07/2019
The CVE-2015-4367 vulnerability represents a critical cross-site scripting flaw within the Simple Subscription module for Drupal platforms, affecting versions prior to 6.x-1.1 and 7.x-1.x before 7.x-1.1. This vulnerability specifically targets authenticated users who possess the "administer blocks" permission, creating a significant security risk for Drupal-based web applications. The flaw resides in how the module handles block content input, allowing malicious actors to inject arbitrary web scripts or HTML code that can be executed in the browsers of other users. The vulnerability classification aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, making it a prime example of insecure input handling that can lead to widespread client-side exploitation. The attack vector is particularly concerning because it leverages legitimate administrative permissions, meaning that an attacker who has gained access to an account with block administration privileges can exploit this weakness to compromise other users within the same Drupal environment.
The technical implementation of this vulnerability stems from insufficient output sanitization within the Simple Subscription module's handling of block content fields. When administrators create or modify blocks through the Drupal interface, the module fails to properly escape or filter user-supplied content before rendering it on web pages. This inadequate sanitization allows attackers to embed malicious scripts that execute in the context of other users' browsers when they view pages containing the compromised block content. The vulnerability demonstrates a classic case of improper input validation and output encoding, where the system trusts user input without sufficient sanitization measures. The impact is amplified by the fact that the affected module operates within the core Drupal framework, meaning that successful exploitation can potentially affect multiple pages and user sessions across the entire website. From an operational perspective, this vulnerability creates a persistent threat vector that can be exploited to steal session cookies, perform unauthorized actions on behalf of users, or redirect victims to malicious websites, making it particularly dangerous for organizations relying on Drupal for their web presence.
The operational impact of CVE-2015-4367 extends beyond simple script injection, as it provides attackers with a foothold for more sophisticated attacks within the Drupal environment. Once an attacker successfully injects malicious code through the vulnerable block content, they can leverage this capability to establish persistent access patterns or conduct phishing attacks against other users. The vulnerability's classification under the ATT&CK framework would fall under the T1059.007 technique for 'Command and Scripting Interpreter: JavaScript', as it enables the execution of JavaScript code within victim browsers. Organizations using affected Drupal versions face significant risk of data breaches, session hijacking, and potential lateral movement within their network infrastructure if the compromised Drupal installation is connected to other systems. The vulnerability also represents a failure in the principle of least privilege, as it allows a relatively low-impact permission level to create high-impact security consequences. Security teams must consider this vulnerability as part of a broader attack surface assessment, particularly when evaluating the security posture of content management systems that rely heavily on user-generated content and block-based layouts.
Mitigation strategies for CVE-2015-4367 focus primarily on immediate version upgrades and access control measures. Organizations should immediately upgrade to the patched versions of the Simple Subscription module for both Drupal 6 and 7 branches, as these releases contain the necessary security fixes to prevent the XSS injection vectors. In addition to version updates, administrators should implement strict access controls to limit the number of users who possess the "administer blocks" permission, reducing the attack surface for potential exploitation. Input validation and output encoding measures should be reinforced throughout the Drupal installation, particularly in areas where user-generated content is rendered. The implementation of Content Security Policy (CSP) headers can provide an additional layer of protection against script injection attacks, even if the underlying vulnerability is not fully patched. Security monitoring should include detection of suspicious block content modifications and anomalous user behavior that might indicate exploitation attempts. Organizations should also conduct comprehensive security assessments of their Drupal installations to identify other potentially vulnerable modules or custom code that might share similar input handling flaws. Regular security audits and vulnerability scanning should be implemented to maintain ongoing protection against similar threats in the future. The vulnerability serves as a reminder of the critical importance of keeping content management systems updated and maintaining robust security practices around user permissions and input validation.