CVE-2009-3437 in Markdown Preview
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the live preview feature in the Markdown Preview module 6.x for Drupal allows remote attackers to inject arbitrary web script or HTML via "Markdown input."
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Analysis
by VulDB Data Team • 12/25/2017
The CVE-2009-3437 vulnerability represents a critical cross-site scripting flaw within the Drupal content management system's Markdown Preview module version 6.x. This vulnerability specifically targets the live preview functionality that allows users to see formatted content before publishing. The issue arises from inadequate input sanitization mechanisms within the module's processing pipeline, creating an exploitable vector for malicious actors to inject arbitrary web scripts or HTML content. The vulnerability affects Drupal 6.x installations where the Markdown Preview module is enabled, making it particularly concerning given the widespread adoption of this CMS version during that period.
The technical exploitation of this vulnerability occurs through the Markdown input processing mechanism where user-supplied content containing malicious scripts is not properly filtered or escaped before being rendered in the live preview interface. When a user submits Markdown content that includes embedded javascript or html tags, the module fails to adequately sanitize this input, allowing the malicious code to execute within the context of other users' browsers. This flaw falls under CWE-79, which specifically addresses cross-site scripting vulnerabilities, and demonstrates how insecure input handling can lead to complete session hijacking and data theft. The vulnerability is particularly dangerous because it leverages the legitimate preview functionality that users expect to work seamlessly, making it difficult to distinguish between benign and malicious content.
From an operational perspective, this vulnerability creates significant risks for Drupal websites that rely on user-generated content or collaborative editing features. Attackers can exploit this weakness to steal user sessions, redirect visitors to malicious sites, or deface websites by injecting persistent scripts into the preview functionality. The impact extends beyond simple data theft to include potential privilege escalation if the affected Drupal installation has administrative users who view the preview content. This vulnerability directly maps to ATT&CK technique T1566, which covers social engineering through malicious content injection, and represents a classic example of how seemingly benign features can become attack vectors when proper security controls are absent.
Organizations affected by this vulnerability should immediately implement several mitigation strategies to protect their Drupal installations. The primary recommendation involves upgrading to the patched version of the Markdown Preview module or disabling the module entirely if live preview functionality is not essential. Additionally, implementing proper input validation and output encoding mechanisms within the application's content processing pipeline can help prevent similar issues in other modules. Security headers such as Content-Security-Policy should be configured to limit script execution capabilities, and regular security audits should be conducted to identify other potential XSS vulnerabilities. The vulnerability underscores the importance of maintaining updated security practices and the necessity of thorough input sanitization across all user-facing features, particularly those that process rich text or markup content.