CVE-2015-9509 in Content Restriction Extension
Summary
by MITRE
The Easy Digital Downloads (EDD) Content Restriction 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-2015-9509 represents a cross-site scripting flaw in the Easy Digital Downloads Content Restriction extension for WordPress platforms. This security issue affects multiple versions of the EDD plugin, specifically targeting versions 1.8.x before 1.8.7, 1.9.x before 1.9.10, 1.0.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. The flaw stems from improper usage of the add_query_arg WordPress function, which creates a pathway for malicious actors to inject arbitrary JavaScript code into the application's output streams. This misimplementation allows attackers to execute scripts in the context of other users' browsers, potentially compromising user sessions and data integrity. The vulnerability operates at the application layer and specifically targets the content restriction functionality that EDD provides for managing access to digital downloads.
The technical root cause of this vulnerability can be classified as CWE-79 Cross-site Scripting, which occurs when an application incorporates untrusted data into web pages without proper validation or escaping mechanisms. The misuse of add_query_arg function in the Content Restriction extension demonstrates a classic improper input handling pattern where user-supplied parameters are directly incorporated into URL generation without adequate sanitization. This flaw enables attackers to inject malicious scripts through URL parameters that are then processed by the add_query_arg function, which fails to properly escape or validate the input before inclusion in the HTML output. The vulnerability is particularly concerning because it leverages WordPress's built-in URL manipulation functions in an insecure manner, making it difficult for administrators to detect and prevent through standard security monitoring.
The operational impact of this vulnerability extends beyond simple script execution, as it can lead to complete session hijacking, unauthorized access to user accounts, and potential data breaches within affected WordPress installations. Attackers can craft malicious URLs that, when visited by authenticated users, execute scripts that steal cookies, modify content, or redirect users to malicious sites. The vulnerability affects both administrators and regular users who may encounter the malicious content while browsing restricted download areas or accessing content that has been processed through the affected extension. The widespread use of Easy Digital Downloads across WordPress platforms means that numerous websites handling digital commerce could be compromised, potentially leading to financial losses, reputational damage, and legal consequences. This vulnerability also aligns with ATT&CK technique T1566.001 which involves social engineering through malicious links, making it particularly dangerous in environments where users regularly interact with download content.
Mitigation strategies for CVE-2015-9509 primarily involve immediate patching of the affected EDD versions to the latest secure releases, specifically upgrading to versions 1.8.7, 1.9.10, 2.0.5, 2.1.11, 2.2.9, and 2.3.7 respectively. System administrators should also implement input validation measures and ensure that all user-supplied parameters are properly sanitized before being processed through WordPress functions. Network monitoring solutions should be configured to detect suspicious URL patterns that might indicate exploitation attempts, and web application firewalls can be deployed to filter out known malicious payloads. Additionally, organizations should conduct comprehensive security audits of their WordPress installations to identify any other potentially vulnerable plugins or themes that might be using similar patterns of insecure parameter handling. The vulnerability highlights the importance of proper input validation and output escaping practices, particularly when dealing with URL generation functions, and reinforces the need for regular security updates and vulnerability assessments in WordPress environments.