CVE-2011-3855 in F8 Lite
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the F8 Lite theme before 4.2.2 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-2011-3855 vulnerability represents a critical cross-site scripting flaw in the F8 Lite WordPress theme, specifically affecting versions prior to 4.2.2. This vulnerability resides within the theme's handling of user input through the s parameter, which is commonly used for search functionality on WordPress sites. The flaw enables remote attackers to execute malicious scripts in the context of other users' browsers, potentially compromising the security of entire WordPress installations that utilize this vulnerable theme. The vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is classified as a fundamental web application security weakness that has been consistently ranked among the top ten web application security risks by OWASP.
The technical implementation of this vulnerability occurs when the F8 Lite theme fails to properly sanitize or escape user input received through the search parameter s. When a user submits a search query containing malicious script code, the theme processes this input without adequate validation or output encoding, allowing the malicious payload to be executed in the browser of any user who views the search results page. This unfiltered input processing creates an environment where attackers can inject HTML content, JavaScript code, or other malicious scripts that execute within the context of legitimate user sessions. The vulnerability specifically exploits the theme's template files that handle search functionality, making it particularly dangerous as search parameters are frequently accessed and displayed on public-facing WordPress sites.
The operational impact of CVE-2011-3855 extends beyond simple script injection, potentially enabling sophisticated attack vectors that can lead to session hijacking, credential theft, and full compromise of user accounts. Attackers can leverage this vulnerability to create persistent backdoors, redirect users to malicious sites, or manipulate content displayed to other visitors. The vulnerability affects WordPress sites using the F8 Lite theme, which represents a significant portion of the WordPress ecosystem at the time of the flaw's discovery, making it a prime target for automated exploitation. Security researchers have documented similar patterns in the ATT&CK framework under the technique of web application attacks, where persistent XSS vulnerabilities are commonly used to establish long-term access to compromised systems and facilitate data exfiltration.
Mitigation strategies for CVE-2011-3855 primarily focus on immediate theme updates to version 4.2.2 or later, which contains the necessary patches to properly sanitize search parameter input. System administrators should also implement additional security measures including input validation, output encoding, and regular security audits of installed themes and plugins. The vulnerability demonstrates the importance of maintaining up-to-date WordPress themes and plugins, as well as implementing proper content security policies to prevent unauthorized script execution. Organizations should also consider implementing web application firewalls and monitoring for suspicious search queries that may indicate attempted exploitation of similar vulnerabilities. The remediation process involves not only updating the vulnerable theme but also reviewing other theme components for similar input handling issues that may present additional attack surfaces.