CVE-2015-9511 in Conditional Success Redirects Extension
Summary
by MITRE
The Easy Digital Downloads (EDD) Conditional Success Redirects 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-2015-9511 affects the Easy Digital Downloads WordPress plugin ecosystem, specifically targeting the Conditional Success Redirects extension that enables dynamic redirection based on purchase conditions. This security flaw exists in multiple versions of the Easy Digital Downloads plugin spanning from 1.8.x through 2.3.x, creating a widespread exposure across numerous WordPress installations that rely on this e-commerce functionality. The vulnerability manifests as a cross-site scripting flaw that undermines the integrity of user sessions and potentially exposes sensitive data within the WordPress administrative environment. The affected versions include critical releases such as 1.8.6, 1.9.9, 2.0.4, 2.1.10, 2.2.8, and 2.3.6, indicating that the flaw persisted across major version branches and required multiple patch releases to address.
The technical root cause stems from improper implementation of the add_query_arg WordPress function within the extension's redirect handling logic. This misuse allows malicious actors to inject arbitrary JavaScript code through carefully crafted query parameters that are subsequently processed and executed in the browser context of authenticated users. The vulnerability specifically exploits the lack of proper input sanitization and output encoding when handling user-supplied parameters in redirect URLs, creating an attack surface where reflected cross-site scripting can occur. The flaw operates by accepting user-controllable input through URL parameters and directly incorporating this data into redirect logic without adequate validation or sanitization measures, making it particularly dangerous in the context of e-commerce transactions where users might be redirected to malicious sites.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform session hijacking, steal administrative credentials, or redirect users to phishing sites that appear legitimate. An attacker could craft malicious URLs that, when clicked by an authenticated administrator, would execute malicious JavaScript code within the context of the WordPress admin interface. This could lead to complete compromise of the WordPress installation, allowing unauthorized modification of product catalogs, access to customer data, or even full administrative control over the e-commerce platform. The vulnerability is particularly concerning because it affects the redirect functionality that is commonly used in payment processing flows, making it an attractive target for attackers seeking to intercept sensitive transactional data or manipulate user experiences during checkout processes.
Mitigation strategies for CVE-2015-9511 require immediate patching of affected versions to the latest available releases, with particular attention to upgrading from vulnerable versions such as 1.8.6 through 2.3.6. Organizations should implement proper input validation and output encoding mechanisms to prevent similar issues in custom code development, following established security guidelines for web application development. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and demonstrates the importance of proper parameter handling in WordPress plugins. Security practitioners should also consider implementing web application firewalls to detect and block suspicious query parameter patterns, while monitoring for unusual redirect behavior in their WordPress installations. Regular security audits of third-party plugins and adherence to security best practices such as those outlined in the OWASP Top Ten and NIST cybersecurity guidelines are essential for preventing similar vulnerabilities from emerging in the WordPress ecosystem.