CVE-2015-9510 in Cross-sell Upsell Extension
Summary
by MITRE
The Easy Digital Downloads (EDD) Cross-sell Upsell extension for WordPress, as used with EDD 1.8.x before 1.8.7, 1.9.x before 1.9.10, 2.0.x before 2.0.5, 2.1.x before 2.1.11, 2.2.x before 2.2.9, and 2.3.x before 2.3.7, has XSS because add_query_arg is misused.
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Analysis
by VulDB Data Team • 02/08/2025
The vulnerability CVE-2015-9510 represents a cross-site scripting flaw in the Easy Digital Downloads Cross-sell Upsell extension for WordPress, affecting multiple versions of the EDD plugin across various release branches. This issue stems from improper handling of URL parameters within the add_query_arg function, creating a persistent security weakness that allows attackers to inject malicious scripts into web pages viewed by other users. The vulnerability specifically impacts users running EDD versions 1.8.x through 2.3.x before their respective security patches, making it a widespread concern for WordPress sites utilizing this popular e-commerce plugin.
The technical flaw manifests when the add_query_arg function fails to properly sanitize or escape user-supplied input before incorporating it into URL parameters. This misusage creates an environment where malicious actors can craft specially crafted URLs containing script tags or other malicious payloads that get executed in the context of other users' browsers. The vulnerability falls under CWE-79 - Cross-site Scripting, which is classified as a critical weakness in web application security, as it allows attackers to execute arbitrary JavaScript code in victim browsers. The improper implementation of input validation and output encoding creates a direct pathway for attackers to bypass security measures and compromise user sessions or steal sensitive information.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, data exfiltration, and redirection to malicious websites. WordPress administrators running affected versions of the EDD plugin face significant risk since the vulnerability exists within a widely used e-commerce extension that handles sensitive transactional data. The cross-site scripting weakness can be exploited through various attack vectors including malicious links shared via email, social media, or compromised websites, making it particularly dangerous for online stores that rely on customer trust and secure transactions. This vulnerability directly violates the principle of least privilege and can be leveraged to escalate attacks against the entire WordPress installation.
Mitigation strategies for CVE-2015-9510 primarily involve immediate patching of the affected EDD plugin versions to their secure releases, with administrators monitoring for updates from the plugin developers. The recommended approach aligns with ATT&CK technique T1059.007 - Command and Scripting Interpreter: PowerShell, where proper input sanitization and output encoding should be implemented as defensive measures. Security teams should implement proper parameter validation using WordPress core functions like esc_url_raw() or sanitize_text_field() before processing URL parameters. Additionally, implementing Content Security Policy headers can provide an additional layer of protection against script injection attempts. Organizations should also conduct thorough security audits of their WordPress installations, reviewing all plugins for similar vulnerabilities and establishing regular update procedures to prevent future exposure to known security flaws. The vulnerability demonstrates the critical importance of proper input validation in web applications and highlights the need for security-conscious development practices throughout the software lifecycle.