CVE-2015-9513 in Favorites Extension
Summary
by MITRE
The Easy Digital Downloads (EDD) Favorites 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 CVE-2015-9513 vulnerability affects the Easy Digital Downloads Favorites extension for WordPress, representing a cross-site scripting flaw that emerged in multiple versions of the EDD plugin ecosystem. This vulnerability specifically targets the misimplementation of the add_query_arg function within the favorites extension, creating a persistent security risk for WordPress installations that utilize this particular plugin functionality. The affected versions span across major release branches including 1.8.x through 2.3.x, indicating a widespread impact across the plugin's lifecycle and suggesting that the flaw was either introduced early in the development cycle or remained undetected for an extended period.
The technical flaw stems from improper handling of user-supplied input within the add_query_arg function, which is designed to manipulate URL query parameters in WordPress environments. When users interact with the favorites functionality, the extension fails to properly sanitize or escape query arguments before incorporating them into dynamic URLs or HTML output contexts. This misusage creates an environment where malicious actors can inject arbitrary JavaScript code through crafted query parameters, which then executes in the context of other users' browsers who visit pages containing these manipulated URLs. The vulnerability operates at the application layer and requires user interaction to be exploited, making it classified as a client-side attack vector that leverages the trust relationship between users and the web application.
The operational impact of this vulnerability extends beyond simple data theft or session hijacking, as it enables attackers to perform a range of malicious activities through the compromised WordPress installation. An attacker could potentially redirect users to phishing sites, inject malicious advertisements, or execute persistent JavaScript payloads that modify the behavior of the website. The vulnerability affects not just individual user sessions but could compromise the entire WordPress installation's integrity, especially when combined with other exploitation techniques or when the vulnerable site handles sensitive user data. The fact that this affects multiple major version branches indicates that the core flaw was fundamental to the implementation rather than a one-time coding error, making the remediation efforts more extensive across the plugin's user base.
Mitigation strategies for CVE-2015-9513 require immediate patching of affected versions to the latest stable releases where the vulnerability has been addressed through proper input sanitization and query parameter handling. Organizations should implement comprehensive security monitoring to detect potential exploitation attempts and establish automated patch management processes to ensure timely updates across all WordPress installations. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and can be mapped to ATT&CK technique T1566.001 for the initial compromise through malicious web content. Additionally, implementing Content Security Policy headers and regular security audits of third-party plugins can help prevent similar issues from arising in the future, while also providing defense-in-depth measures against exploitation attempts that may target unpatched systems or zero-day vulnerabilities in the WordPress ecosystem.