CVE-2015-6969 in Serendipity
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in js/2k11.min.js in the 2k11 theme in Serendipity before 2.0.2 allows remote attackers to inject arbitrary web script or HTML via a user name in a comment, which is not properly handled in a Reply link.
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Analysis
by VulDB Data Team • 06/15/2022
The CVE-2015-6969 vulnerability represents a critical cross-site scripting flaw in the 2k11 theme of Serendipity blogging platform versions prior to 2.0.2. This vulnerability resides within the js/2k11.min.js JavaScript file and specifically targets the handling of user names in comment reply functionality. The flaw allows remote attackers to execute malicious scripts by injecting arbitrary web content through user names entered in comments, creating a persistent security risk for blog administrators and visitors. The vulnerability operates by failing to properly sanitize or escape user input before incorporating it into dynamic HTML elements, particularly Reply links that reference user names. This represents a classic XSS attack vector where attacker-controlled data flows directly into the browser without proper validation or encoding mechanisms.
The technical implementation of this vulnerability demonstrates poor input validation practices within the theme's JavaScript code. When users submit comments containing user names, the system fails to implement proper HTML escaping or sanitization routines before embedding these names into Reply links. The attack exploits the fact that the JavaScript code constructs HTML elements dynamically using user-provided data without adequate security measures. This flaw falls under CWE-79 - Improper Neutralization of Input During Web Page Generation, which is a fundamental weakness in web application security. The vulnerability specifically affects the Reply link functionality where user names are embedded into href attributes or other HTML properties, making it susceptible to script injection attacks.
The operational impact of CVE-2015-6969 extends beyond simple script execution, as it enables attackers to potentially hijack user sessions, steal sensitive information, or redirect users to malicious websites. When exploited, the vulnerability allows attackers to create malicious Reply links that execute arbitrary JavaScript code in the context of other users' browsers, potentially leading to account takeovers or data exfiltration. The persistent nature of this vulnerability means that any user name entered in comments could become a vector for attack, making it particularly dangerous in public comment systems. This vulnerability also aligns with ATT&CK technique T1566.001 - Phishing: Spearphishing Attachment, as attackers could craft malicious user names that, when clicked, would execute harmful code in the victim's browser. The vulnerability affects not only the immediate comment functionality but also potentially impacts the broader security posture of the blogging platform.
The recommended mitigations for this vulnerability include immediate upgrading to Serendipity version 2.0.2 or later, which contains the necessary patches to address the XSS flaw. Additionally, administrators should implement comprehensive input validation and sanitization measures for all user-provided data, particularly in comment systems and dynamic content generation. The fix typically involves implementing proper HTML escaping routines before embedding user data into JavaScript or HTML contexts, ensuring that special characters are properly encoded to prevent script execution. Security practitioners should also consider implementing Content Security Policy headers to limit script execution capabilities and employ regular security audits of JavaScript files to identify similar input handling issues. Organizations using older versions of Serendipity should implement temporary workarounds such as disabling comment features or implementing additional filtering layers to prevent exploitation of this vulnerability.