CVE-2026-76564 in Cart Extension
Summary
by MITRE • 08/20/2026
Joomla Extension - phoca.cz - Stored XSS via User-Agent header in Admin Order View in Phoca Cart 5.0.0-6.1.7
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Analysis
by VulDB Data Team • 08/20/2026
The vulnerability identified as a stored cross-site scripting (XSS) flaw within the Phoca Cart extension for Joomla versions 5.0.0 through 6.1.7 represents a significant security risk to e-commerce platforms relying on this software. The core of the issue lies in how the application processes HTTP request headers, specifically the User-Agent string, when rendering administrative interface components. In typical web applications, the User-Agent header is used for browser detection and analytics logging rather than direct display within sensitive administrative views. However, in the Admin Order View module of Phoca Cart, this input vector was not adequately sanitized before being rendered into the HTML output. This lack of proper validation allows an attacker to inject malicious JavaScript code directly into the stored data structure associated with order records or session logs that are subsequently displayed by administrators.
From a technical perspective, this vulnerability is classified under CWE-79, which denotes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. The specific subtype here involves reflected input being persisted in a database and later retrieved for display without proper encoding or escaping. When an administrator accesses the order details page, the application retrieves the stored User-Agent string from the backend storage and injects it into the DOM of the administrative dashboard. Because modern browsers execute JavaScript embedded within HTML content by default, any script tags, event handlers, or other executable payloads contained within the maliciously crafted User-Agent header will run in the context of the administrator's session. This execution occurs with the privileges of the logged-in user, who typically possesses elevated permissions including access to customer data, order management functions, and potentially system configuration settings.
The operational impact of this vulnerability is severe due to its stored nature. Unlike reflected XSS which requires tricking a user into clicking a malicious link, stored XSS persists on the server side. This means that every time an administrator views the affected page, the payload executes automatically without further interaction from the attacker beyond the initial injection phase. An adversary can exploit this by crafting a request with a specially formatted User-Agent header containing JavaScript code designed to steal session cookies, perform actions on behalf of the admin such as modifying product prices or exporting customer databases, or redirecting the administrator to phishing sites. The persistence of the payload ensures that multiple administrators may be compromised if they access the vulnerable view, leading to widespread credential theft and potential full compromise of the Joomla instance depending on the administrative privileges held by those users.
This attack vector aligns with MITRE ATT&CK techniques related to Client-side Scripting Injection (T1059) and potentially Credential Access via Browser Session Hijacking if session tokens are exfiltrated. The vulnerability highlights a common oversight in web application development where input from less obvious sources like HTTP headers is treated as trusted data for display purposes. Developers often focus on sanitizing form inputs while neglecting to apply the same rigorous validation standards to header values, assuming they are immutable or non-malicious. In this case, the failure to encode special characters such as angle brackets and quotes in the User-Agent string before rendering it in an HTML context allowed for successful code injection.
Mitigation strategies must address both immediate remediation and long-term defensive coding practices. The primary solution is to apply strict output encoding when rendering any user-supplied data into HTML, particularly within administrative interfaces where trust assumptions are often relaxed incorrectly. Developers should utilize established libraries that handle character escaping according to the context in which the data is being inserted, such as HTML entity encoding for general text or JavaScript-specific escaping if the value were ever embedded in a script block. Additionally, implementing Content Security Policy (CSP) headers can significantly reduce the impact of successful XSS attacks by restricting the sources from which scripts are allowed to load and execute, thereby preventing inline script execution even if injection occurs. Upgrading to patched versions of Phoca Cart that have addressed this specific input validation gap is essential for immediate risk reduction. Furthermore, conducting regular security audits focused on input handling across all request components, including headers like User-Agent, Referer, and Cookie, will help identify similar vulnerabilities in other parts of the application ecosystem.