CVE-2026-104479 in Shopclass
Summary
by MITRE • 10/03/2026
Shopclass before 6.2.0 contains a stored cross-site scripting vulnerability that allows self-registered non-admin users to inject scripts into item listing descriptions when frontend TinyMCE is enabled. Attackers can submit malicious JavaScript, which ItemActions.php saves without tag stripping, causing it to execute in the site origin for any visitor viewing the listing.
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Analysis
by VulDB Data Team • 10/03/2026
The vulnerability identified in Shopclass versions prior to 6.2.0 represents a critical security flaw classified as a Stored Cross-Site Scripting (XSS) issue. This type of vulnerability occurs when an application stores malicious script content on its server, which is then served to other users without proper sanitization or encoding. In this specific instance, the attack vector targets item listing descriptions within the platform's frontend interface. The root cause lies in the improper handling of user-supplied input by the ItemActions.php component, specifically when the TinyMCE rich text editor is enabled on the front end. Unlike reflected XSS where malicious scripts are executed immediately via a crafted link, stored XSS persists because the payload is saved to the database and subsequently rendered for every visitor who views the affected listing, creating a persistent threat that does not require direct interaction with the attacker after initial submission.
The technical mechanism of this flaw involves a failure in input validation and output encoding processes. When non-admin users register on the platform and attempt to create or edit item listings, they are provided access to the TinyMCE editor for formatting their descriptions. The application accepts HTML content from this editor but fails to strip potentially dangerous script tags or attributes before saving them to the backend storage via ItemActions.php. Consequently, when a victim user navigates to view an affected listing, the browser parses the stored malicious JavaScript as part of the page's Document Object Model (DOM). Because the scripts execute in the context of the site’s origin, they inherit all cookies, session tokens, and access privileges associated with that domain. This allows attackers to perform actions on behalf of victims, steal sensitive information such as authentication credentials or personal data, deface web pages, or redirect users to malicious external sites designed for phishing attacks.
From an operational perspective, the impact of this vulnerability is severe due to its self-propagating nature and low barrier to entry. Since any non-admin user can exploit it by simply registering on the platform, there are no complex privilege escalation steps required to initiate the attack. The persistence of the payload means that a single successful injection can compromise numerous users over an extended period until the malicious content is manually removed or patched. This significantly increases the blast radius compared to transient vulnerabilities. Furthermore, because the execution occurs in the context of the legitimate site origin, traditional browser security policies like Same-Origin Policy do not prevent the script from accessing local storage, cookies, or performing AJAX requests to internal APIs that might be available only to authenticated users.
To mitigate this vulnerability and align with industry best practices such as those defined by the Common Weakness Enumeration (CWE) and MITRE ATT&CK framework, immediate remediation is required. The primary mitigation involves upgrading Shopclass to version 6.2.0 or later where these input validation flaws have been addressed. From a defensive coding perspective, developers must implement strict output encoding for all dynamic content rendered in HTML contexts to ensure that special characters are converted into their corresponding entity equivalents, preventing the browser from interpreting them as executable code. Additionally, implementing Content Security Policy (CSP) headers can provide an additional layer of defense by restricting the sources from which scripts can be loaded and executed. Input validation should also be enforced on both client-side and server-side to reject or sanitize any HTML tags that are not explicitly allowed in item descriptions. These measures align with CWE-79, which covers Improper Neutralization of Script-Related HTML Tags in a Web Page, and MITRE ATT&CK technique T1059, specifically subtechnique 007 for JavaScript-based execution.