CVE-2015-5734 in WordPress
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the legacy theme preview implementation in wp-includes/theme.php in WordPress before 4.2.4 allows remote attackers to inject arbitrary web script or HTML via a crafted string.
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Analysis
by VulDB Data Team • 05/08/2018
The vulnerability identified as CVE-2015-5734 represents a critical cross-site scripting flaw within WordPress's legacy theme preview functionality. This issue resides in the wp-includes/theme.php file and affects WordPress versions prior to 4.2.4, making it a significant concern for web application security. The vulnerability stems from insufficient input validation and output sanitization mechanisms that fail to properly handle malicious user-supplied data within the theme preview feature. Attackers can exploit this weakness by crafting specially formatted strings that, when processed by the vulnerable WordPress implementation, execute arbitrary JavaScript code or HTML content in the context of other users' browsers. The attack vector specifically targets the legacy theme preview functionality, which allows administrators and users to preview themes before activation, creating an ideal environment for malicious payload injection.
The technical nature of this vulnerability aligns with CWE-79, which categorizes cross-site scripting as a code injection flaw where untrusted data is improperly incorporated into web pages without proper validation or escaping. This particular implementation flaw demonstrates a classic failure in data sanitization practices within WordPress's core codebase, where user-provided input intended for theme preview operations bypasses essential security controls. The vulnerability operates at the application layer, specifically targeting the theme preview mechanism that was designed to provide a safe environment for administrators to visualize theme changes before deployment. However, the lack of proper input filtering and output encoding creates a pathway for attackers to inject malicious scripts that execute in the browser context of legitimate users who view the preview. The exploitability of this vulnerability is enhanced by the fact that it requires minimal privileges and can be executed through standard web browser interactions.
The operational impact of CVE-2015-5734 extends beyond simple script execution, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, and data exfiltration. When exploited successfully, this vulnerability allows remote attackers to inject persistent scripts that can compromise user sessions, redirect traffic to malicious sites, or harvest sensitive information from users who interact with the compromised WordPress installation. The attack can be particularly devastating in multi-user environments where administrators frequently use the theme preview feature, as the malicious scripts can target all users who view the previewed content. The vulnerability also poses risks to WordPress installations that may have administrative privileges, as successful exploitation could lead to complete compromise of the web application and potentially the underlying server infrastructure. Organizations running vulnerable WordPress versions face significant risk of unauthorized access, data breaches, and potential lateral movement within their network infrastructure.
Mitigation strategies for CVE-2015-5734 primarily focus on immediate version upgrades to WordPress 4.2.4 or later, which contain the necessary patches to address the XSS vulnerability in the theme preview implementation. System administrators should prioritize patch management and ensure all WordPress installations are updated to the latest stable releases, as this vulnerability has been widely exploited in the wild. Additional protective measures include implementing proper input validation at multiple layers, utilizing web application firewalls to detect and block malicious payloads, and conducting regular security audits of WordPress installations. Organizations should also consider implementing content security policies to limit script execution capabilities and disable unnecessary preview features where possible. The vulnerability highlights the importance of maintaining up-to-date software and following security best practices such as the principle of least privilege, regular security assessments, and comprehensive monitoring of web application traffic for suspicious activities. Security teams should also establish incident response procedures specifically designed to address XSS vulnerabilities and ensure rapid deployment of patches across all affected systems.