CVE-2015-9369 in Easy US Sales Taxes Add-on for iThemes Exchange
Summary
by MITRE
Easy US Sales Taxes 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-2015-9369 affects the Easy US Sales Taxes Add-on for iThemes Exchange plugin, which is designed to handle tax calculations for WordPress e-commerce sites. This plugin version prior to 1.1.0 contains a cross-site scripting vulnerability that stems from improper handling of user input within the add_query_arg() and remove_query_arg() functions. The issue represents a classic input validation flaw that allows malicious actors to inject arbitrary JavaScript code into web pages viewed by other users. The vulnerability specifically manifests when the plugin processes URL parameters that are not properly sanitized or escaped before being rendered in the browser context.
The technical exploitation of this vulnerability occurs through the manipulation of query string parameters that are processed by WordPress's add_query_arg() and remove_query_arg() functions. These functions are commonly used to modify URL parameters within WordPress applications, but in this case, they fail to adequately sanitize input data. When a user visits a page that contains unfiltered query parameters, the malicious JavaScript code injected through these parameters executes in the context of other users' browsers. This creates a persistent XSS vector that can be leveraged to steal session cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users. The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws in web applications.
The operational impact of this vulnerability extends beyond simple script execution as it compromises the integrity and confidentiality of the affected WordPress site. Attackers can exploit this flaw to gain unauthorized access to user sessions, potentially leading to full administrative control of the website. The vulnerability affects not only the plugin's functionality but also the broader security posture of the WordPress installation, as the malicious code can be used to establish persistent backdoors or to harvest sensitive information from authenticated users. The attack surface is particularly concerning because it affects the tax calculation functionality that is likely used by legitimate customers during the checkout process, making it difficult to detect malicious activity. This vulnerability also relates to ATT&CK technique T1059.007 which involves the use of script-based languages for execution.
Mitigation strategies for CVE-2015-9369 should begin with immediate patching of the affected plugin to version 1.1.0 or later, which contains the necessary security fixes. Administrators should implement proper input validation and output encoding for all user-supplied data, particularly when processing URL parameters. The WordPress security hardening practices should include regular plugin updates, implementation of web application firewalls, and monitoring for suspicious user activities. Additionally, network administrators should consider implementing content security policies that restrict the execution of inline scripts and limit the sources from which scripts can be loaded. The vulnerability also highlights the importance of secure coding practices in WordPress plugins, emphasizing the need for proper sanitization of all input data and careful handling of URL parameter manipulation functions. Organizations should conduct regular security audits of their WordPress installations to identify and remediate similar vulnerabilities that may exist in other plugins or themes.