CVE-2015-9523 in Recommended Products extension
Summary
by MITRE
The Easy Digital Downloads (EDD) Recommended Products 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-2015-9523 affects the Easy Digital Downloads WordPress plugin ecosystem, specifically targeting the Recommended Products extension that integrates with various versions of the core EDD plugin. This security flaw represents a classic cross-site scripting vulnerability that arises from improper handling of URL parameters within the plugin's codebase. The vulnerability exists across multiple version ranges of the EDD plugin, indicating a widespread issue that impacted users of the platform from version 1.8.x through 2.3.x, making it particularly concerning for the large user base that relied on this e-commerce solution for WordPress websites.
The technical root cause of this vulnerability stems from the misuse of the WordPress add_query_arg function, which is designed to safely manipulate URL query parameters. When developers improperly implement this function, they can inadvertently introduce XSS vectors by failing to properly sanitize or escape user-controllable input before incorporating it into dynamic URLs. The vulnerability occurs because the plugin fails to adequately validate or escape query string parameters that are passed through the Recommended Products functionality, allowing malicious actors to inject malicious scripts into URLs that are then executed in the browsers of unsuspecting users. This misimplementation creates a pathway for attackers to inject JavaScript code that executes in the context of other users' browsers when they visit pages containing the vulnerable extension.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform various malicious activities including session hijacking, data theft, and redirection to malicious sites. An attacker could craft specially crafted URLs that, when clicked by a victim, would execute malicious JavaScript code in the victim's browser, potentially stealing cookies, session tokens, or other sensitive information. The vulnerability is particularly dangerous because it leverages legitimate plugin functionality, making it difficult for users to distinguish between normal plugin behavior and malicious activity. The widespread adoption of EDD across WordPress installations meant that a successful exploitation could potentially affect numerous websites simultaneously, creating a significant risk for both individual users and website operators who rely on this platform for their online commerce operations.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected versions, with users upgrading to the patched versions 1.8.7, 1.9.10, 2.0.5, 2.1.11, 2.2.9, and 2.3.7 respectively. Organizations should implement comprehensive monitoring of their WordPress installations to identify any instances of the vulnerable plugin versions and ensure all plugins remain updated. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in software, and demonstrates how improper input validation and output encoding can create persistent security weaknesses. From an ATT&CK framework perspective, this vulnerability maps to T1566.001, representing the initial compromise through malicious web content, and could potentially enable further attacks through T1071.001 for command and control communications. Security teams should also consider implementing content security policies and regular security audits to prevent similar issues in other plugins and custom code implementations, while ensuring that all URL parameter handling follows secure coding practices that properly escape or validate user input before incorporating it into dynamic web content.