CVE-2011-3861 in Web Minimalist 200901
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Web Minimalist 200901 theme before 1.2 for WordPress allows remote attackers to inject arbitrary web script or HTML via the PATH_INFO to index.php.
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Analysis
by VulDB Data Team • 02/05/2025
The CVE-2011-3861 vulnerability represents a classic cross-site scripting flaw that specifically targeted the Web Minimalist 200901 WordPress theme version 1.1 and earlier. This vulnerability resides in the theme's handling of HTTP request parameters, particularly the PATH_INFO component that gets passed to the index.php file. The flaw arises from inadequate input validation and output sanitization mechanisms within the theme's codebase, creating an exploitable entry point for malicious actors to inject arbitrary web scripts or HTML content. The vulnerability is particularly concerning because it affects a widely used WordPress theme, making it a prime target for automated attacks and exploitation campaigns.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious URL that includes crafted script content within the PATH_INFO parameter. When the vulnerable WordPress theme processes this request through index.php, the malicious code gets executed in the context of the victim's browser session. This occurs due to the theme's failure to properly sanitize or escape user-supplied input before rendering it in the web page output. The vulnerability is categorized under CWE-79 as "Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')", which directly aligns with the nature of the flaw where untrusted data flows into the web application's output without proper encoding or validation.
The operational impact of this vulnerability extends beyond simple script injection, as it enables attackers to perform various malicious activities including session hijacking, credential theft, defacement of web pages, and redirection to malicious sites. Attackers can leverage this vulnerability to steal cookies, which contain session information that allows them to impersonate legitimate users. The vulnerability affects all users who have the vulnerable theme installed, including administrators, making it particularly dangerous for website owners. Additionally, since this was a theme-level vulnerability rather than a core WordPress vulnerability, it could be exploited even when the WordPress core was updated, as long as the vulnerable theme remained installed.
Mitigation strategies for CVE-2011-3861 primarily involve immediate theme updates to version 1.2 or later, which contained the necessary patches to address the input validation issues. Security practitioners should also implement proper input sanitization at multiple layers including web application firewalls, content security policies, and regular security audits of installed themes and plugins. The vulnerability demonstrates the importance of maintaining up-to-date WordPress themes and plugins, as legacy themes often contain unpatched security flaws. Organizations should also consider implementing CSP headers to limit the execution of unauthorized scripts, which can provide additional protection against similar XSS vulnerabilities. This case highlights the ATT&CK technique of Web Shell Installation through Cross-site Scripting, where attackers can establish persistent access through client-side exploitation, making it essential for security teams to monitor and remediate such vulnerabilities promptly.