CVE-2011-4090 in Serendipity
Summary
by MITRE
Serendipity before 1.6 has an XSS issue in the karma plugin which may allow privilege escalation.
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Analysis
by VulDB Data Team • 01/12/2025
The vulnerability identified as CVE-2011-4090 affects Serendipity versions prior to 1.6 and represents a cross-site scripting flaw within the karma plugin component. This issue arises from inadequate input validation and output encoding mechanisms that fail to properly sanitize user-supplied data before rendering it within the web application interface. The vulnerability exists in the karma plugin which is designed to track user contributions and reputation within the blogging platform, making it a critical component for user interaction and system integrity.
The technical implementation flaw stems from the plugin's failure to employ proper sanitization techniques when processing user input that gets reflected back to the browser without adequate encoding or filtering. This allows malicious actors to inject malicious scripts into the application's response, which can execute in the context of other users' browsers. The vulnerability specifically impacts how the system handles user ratings or karma-related data, where unfiltered input gets directly embedded into HTML output without proper context-aware encoding. This type of vulnerability is categorized under CWE-79 as Cross-Site Scripting, and more specifically aligns with CWE-80 as the failure to sanitize output before rendering in a web page context. The flaw enables attackers to craft malicious payloads that can exploit the trust relationship between the web application and its users.
The operational impact of this vulnerability extends beyond simple script execution to potentially enable privilege escalation within the blogging platform. When users with higher privileges access pages containing the maliciously injected content, the reflected scripts can execute with elevated permissions, allowing attackers to perform actions such as modifying content, creating new administrative accounts, or accessing sensitive user data. The vulnerability creates a persistent threat vector that can be exploited across multiple user sessions, as the malicious script content can be stored and delivered to any user who views the affected pages. This type of attack pattern aligns with ATT&CK technique T1566.001 for Initial Access through Phishing and T1078.004 for Valid Accounts through Cloud Service Accounts, as the exploitation can leverage legitimate user sessions to escalate privileges within the application environment.
Mitigation strategies for CVE-2011-4090 require immediate implementation of proper input validation and output encoding mechanisms throughout the application's data flow. The most effective approach involves applying context-aware encoding to all user-supplied data before rendering it within HTML contexts, particularly in areas where karma values or user ratings are displayed. Organizations should implement strict input validation that filters or rejects suspicious characters and patterns commonly associated with script injection attacks. The recommended solution includes upgrading to Serendipity version 1.6 or later, which contains the necessary security patches and improved sanitization routines. Additionally, implementing Content Security Policy headers can provide an additional layer of protection against script execution, while regular security code reviews and automated vulnerability scanning should be conducted to identify similar issues in other components of the application stack. Security teams should also consider implementing web application firewalls to detect and block suspicious payload patterns that attempt to exploit this type of vulnerability.