CVE-2020-13672 in Drupal
Summary
by MITRE • 02/11/2022
Cross-site Scripting (XSS) vulnerability in Drupal core's sanitization API fails to properly filter cross-site scripting under certain circumstances. This issue affects: Drupal Core 9.1.x versions prior to 9.1.7; 9.0.x versions prior to 9.0.12; 8.9.x versions prior to 8.9.14; 7.x versions prior to 7.80.
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Analysis
by VulDB Data Team • 02/16/2022
The CVE-2020-13672 vulnerability represents a critical cross-site scripting flaw within Drupal core's sanitization API that undermines the application's ability to properly filter malicious script content under specific conditions. This vulnerability affects multiple major versions of the Drupal content management system including the 7.x, 8.9.x, 9.0.x, and 9.1.x branches, creating a widespread impact across numerous deployments. The issue stems from insufficient input validation and output filtering mechanisms that fail to adequately sanitize user-supplied data when processed through Drupal's core sanitization functions. Security researchers identified that under certain circumstances, malicious scripts could bypass the intended filtering processes, potentially allowing attackers to inject harmful code into web pages viewed by other users. This vulnerability operates at the application layer and specifically targets Drupal's HTML sanitization capabilities, which are fundamental to protecting against XSS attacks in web applications.
The technical exploitation of this vulnerability occurs when Drupal processes user input through its sanitization API without proper validation of all possible script injection vectors. The flaw manifests when certain combinations of HTML tags, attributes, and JavaScript code are processed through Drupal's filtering mechanisms, allowing malicious payloads to pass through undetected. This represents a failure in the OWASP Top Ten category of XSS vulnerabilities, specifically categorized under CWE-79: Improper Neutralization of Input During Web Page Generation. The vulnerability can be leveraged by attackers to execute malicious scripts in the context of a victim's browser session, potentially leading to session hijacking, data theft, or unauthorized administrative actions. The issue is particularly concerning because it affects the core sanitization functionality that Drupal relies upon to protect against such attacks, meaning that any module or theme that depends on Drupal's built-in filtering mechanisms could be compromised.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform session hijacking, steal user credentials, or even gain administrative privileges within affected Drupal installations. When exploited successfully, the vulnerability allows attackers to execute arbitrary JavaScript code in the context of other users' browsers, potentially leading to complete compromise of user sessions. The attack surface is broad since Drupal is widely deployed across various industries including government, healthcare, and financial services, making the potential impact substantial. Organizations running affected versions of Drupal must consider the possibility of unauthorized access to sensitive data, modification of website content, and potential lateral movement within their network infrastructure. The vulnerability also aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: JavaScript, as it enables execution of malicious JavaScript payloads that can be used to establish persistent access or perform additional attacks.
Organizations should immediately implement mitigations by upgrading to the patched versions of Drupal core that address this vulnerability, specifically versions 7.80, 8.9.14, 9.0.12, and 9.1.7 or later. Security teams should also consider implementing additional protective measures such as web application firewalls, content security policies, and enhanced input validation at multiple layers of the application architecture. The vulnerability demonstrates the critical importance of proper input sanitization and output encoding in web applications, particularly for content management systems that process user-generated content. Organizations should conduct comprehensive vulnerability assessments to identify any instances of the affected Drupal versions and ensure that all custom modules and themes are also compatible with the patched core versions. Regular security monitoring and patch management processes should be strengthened to prevent similar vulnerabilities from being introduced in the future, as this issue highlights the ongoing challenge of maintaining secure web application frameworks in rapidly evolving threat landscapes.