CVE-2011-3858 in Pixiv Custom
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Pixiv Custom theme before 2.1.6 for WordPress allows remote attackers to inject arbitrary web script or HTML via the s parameter.
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Analysis
by VulDB Data Team • 02/03/2025
The CVE-2011-3858 vulnerability represents a classic cross-site scripting flaw that existed in the Pixiv Custom theme for WordPress platforms prior to version 2.1.6. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is one of the most prevalent and dangerous web application security flaws. The vulnerability specifically affects the theme's handling of user input through the s parameter, which is typically used for search functionality or other dynamic content rendering within the WordPress ecosystem.
The technical implementation of this flaw occurs when the theme fails to properly sanitize or escape user-supplied input before incorporating it into web pages served to end users. When an attacker crafts a malicious payload and submits it through the s parameter, the theme processes this input without adequate validation or encoding measures. This allows the malicious script to execute within the context of other users' browsers who view pages containing the compromised content, potentially leading to session hijacking, credential theft, or further exploitation of the affected WordPress installation.
The operational impact of this vulnerability extends beyond simple script injection, as it provides attackers with a foothold for more sophisticated attacks within the WordPress environment. The attacker can leverage this vulnerability to execute arbitrary JavaScript code in the browsers of other users, potentially stealing cookies, session tokens, or other sensitive information. The vulnerability is particularly concerning because it affects a widely-used WordPress theme, meaning that numerous websites could be compromised simultaneously. According to ATT&CK framework, this vulnerability maps to T1059.007 for Command and Scripting Interpreter, specifically JavaScript, and T1566 for Phishing, as attackers can use this vulnerability to craft malicious payloads that appear legitimate to end users.
The exploitation of this vulnerability typically requires minimal technical skill and can be automated through various attack vectors. Attackers can embed malicious scripts within the s parameter that redirect users to malicious domains, inject tracking code, or perform other malicious activities. The vulnerability is particularly dangerous because it can be exploited through simple web requests without requiring authentication or special privileges. Organizations using the affected theme version should immediately update to version 2.1.6 or later, which implements proper input sanitization and output encoding mechanisms. Additionally, implementing Content Security Policy headers and other web application firewall rules can provide additional defense-in-depth measures to mitigate the risk of exploitation.
This vulnerability demonstrates the critical importance of input validation and output encoding in web application security. The flaw highlights how even seemingly benign functionality like search parameters can become attack vectors when proper security measures are not implemented. The remediation process involves not only updating the theme but also implementing comprehensive security practices including regular security audits, proper input validation, and output encoding for all user-supplied data. Organizations should also consider implementing automated monitoring systems to detect and respond to similar vulnerabilities across their web applications, as the principles underlying this vulnerability are common across many web platforms and frameworks.