CVE-2015-9364 in 2Checkout Add-on for iThemes Exchange
Summary
by MITRE
2Checkout Add-on for iThemes Exchange before 1.1.0 for WordPress has XSS via add_query_arg() and remove_query_arg().
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Analysis
by VulDB Data Team • 12/07/2023
The vulnerability identified as CVE-2015-9364 affects the 2Checkout Add-on for iThemes Exchange plugin version prior to 1.1.0 within the WordPress ecosystem. This security flaw represents a cross-site scripting vulnerability that emerges from improper handling of user-supplied input within the plugin's query argument processing functions. The vulnerability specifically exploits the add_query_arg() and remove_query_arg() WordPress functions which are commonly used to manipulate URL parameters and query strings. These functions are fundamental components in WordPress plugin development for managing dynamic URLs and maintaining state across different pages. The flaw allows attackers to inject malicious scripts into URL parameters that are then executed in the context of other users' browsers when they visit pages containing these manipulated query strings.
The technical implementation of this vulnerability stems from insufficient sanitization and validation of input parameters that are processed through the add_query_arg() and remove_query_arg() functions. When these functions receive untrusted input without proper filtering, they can inadvertently incorporate malicious script code into the generated URLs. This occurs because WordPress core functions do not automatically escape output when query arguments are manipulated, particularly in contexts where the arguments are later rendered in HTML content or JavaScript contexts. Attackers can craft malicious URLs containing script payloads that get stored in the query parameters and subsequently executed when legitimate users browse to pages that process these parameters. The vulnerability is particularly concerning because it operates at the plugin level rather than requiring administrative access, making it exploitable by anyone who can influence URL parameters.
The operational impact of this vulnerability extends beyond simple script execution to potentially enable more sophisticated attacks including session hijacking, data theft, and privilege escalation. When users browse to compromised pages, their browsers execute the injected scripts, which could redirect them to malicious sites, steal cookies and session tokens, or perform actions on their behalf without their knowledge. The vulnerability affects any WordPress site running the vulnerable plugin version, creating a widespread attack surface since iThemes Exchange is a popular e-commerce plugin. Users with administrative privileges are particularly at risk as the malicious scripts could potentially leverage their elevated permissions to perform unauthorized actions. The attack vector is relatively simple to exploit since it only requires manipulation of URL parameters that are commonly used in web applications.
Mitigation strategies for CVE-2015-9364 should focus on immediate plugin updates to version 1.1.0 or later, which contain the necessary patches to address the XSS vulnerability. System administrators should also implement proper input validation and output escaping mechanisms when working with query arguments in WordPress plugins, following established security practices such as those outlined in the OWASP Top Ten and CWE-79. The principle of least privilege should be applied by ensuring that plugin functions do not have unnecessary access to query parameters that could be manipulated by attackers. Additionally, implementing Content Security Policy headers can provide an additional layer of protection against script execution even if the vulnerability is exploited. Regular security audits of WordPress plugins should be conducted to identify similar vulnerabilities, with particular attention to functions that manipulate URL parameters and handle user input. This vulnerability aligns with CWE-79 which categorizes cross-site scripting flaws and demonstrates the importance of proper input sanitization and output encoding in web applications.
The attack surface for this vulnerability can be further reduced by implementing proper URL parameter validation at multiple layers of the application architecture. WordPress developers should adopt secure coding practices that include escaping output when query arguments are rendered in HTML contexts, using wp_kses() or similar sanitization functions to prevent malicious content from being executed. The vulnerability also highlights the importance of security testing during plugin development, particularly in areas where user input is processed through core WordPress functions. Organizations should maintain updated security baselines and regularly monitor for vulnerabilities in their WordPress installations, particularly in third-party plugins that may not receive timely security updates. The remediation process should include not only updating the vulnerable plugin but also reviewing other plugins that may use similar query argument handling patterns to ensure they are not susceptible to similar vulnerabilities.