CVE-2025-41052: Apprain CMF Stored XSS Vulnerability

CVE-2025-41052 Overview

CVE-2025-41052 is a stored cross-site scripting (XSS) vulnerability in appRain CMF version 4.0.5. The flaw resides in the /apprain/developer/addons/update/canvasjs endpoint, which fails to validate input submitted through the data[Addon][layouts] and data[Addon][layouts_except] parameters. An authenticated attacker can inject persistent JavaScript payloads that execute in the browser of any user who later views the affected page. The vulnerability is tracked under CWE-79: Improper Neutralization of Input During Web Page Generation.

Critical Impact
Authenticated attackers can store arbitrary JavaScript that runs in victim browsers, enabling session theft, administrative action hijacking, and content tampering within the appRain CMF administrative interface.

Affected Products

appRain CMF version 4.0.5
Deployments exposing /apprain/developer/addons/update/canvasjs to authenticated users
Instances where multiple user roles share access to the developer addons module

Discovery Timeline

2025-09-04 - CVE-2025-41052 published to the National Vulnerability Database
2026-09-30 - Last updated in the NVD database

Technical Details for CVE-2025-41052

Vulnerability Analysis

The vulnerability is a stored XSS flaw in the appRain CMF addon update workflow. When a user submits data to /apprain/developer/addons/update/canvasjs, the application accepts the data[Addon][layouts] and data[Addon][layouts_except] parameters without applying output encoding or input sanitization. The injected payload is persisted in the addon configuration and rendered back to users who access the module. Because the payload executes in an authenticated administrative context, an attacker can leverage victim privileges to perform actions such as modifying addons, altering content, or exfiltrating session cookies. Exploitation requires low attacker privileges and user interaction from the victim, which aligns with the medium severity rating. Further technical context is available in the INCIBE Security Notice on appRain CMF Vulnerabilities.

Root Cause

The root cause is missing input validation and output encoding on the data[Addon][layouts] and data[Addon][layouts_except] parameters. The application stores raw user-supplied content and later emits it into HTML responses without neutralizing script-bearing characters, which satisfies the conditions for stored XSS under CWE-79.

Attack Vector

An authenticated attacker sends a crafted POST request to /apprain/developer/addons/update/canvasjs with a JavaScript payload embedded in data[Addon][layouts] or data[Addon][layouts_except]. The payload is persisted server-side. When another authenticated user, such as an administrator, loads the affected addon view, the browser renders the stored payload and executes the attacker-controlled script in the victim's session context.

// No verified public exploit code is available for CVE-2025-41052.
// Refer to the INCIBE advisory for additional technical detail.

Detection Methods for CVE-2025-41052

Indicators of Compromise

Entries in appRain CMF addon configuration records containing <script>, onerror=, onload=, or javascript: sequences in the layouts or layouts_except fields
HTTP POST requests to /apprain/developer/addons/update/canvasjs with payload characters such as <, >, or encoded equivalents in the data[Addon][layouts] or data[Addon][layouts_except] parameters
Unexpected outbound requests from administrator browsers to attacker-controlled domains shortly after accessing the developer addons module

Detection Strategies

Inspect web server access logs for POST requests to the vulnerable endpoint and correlate request bodies with suspicious markup
Review the appRain CMF database for persisted addon records containing HTML or JavaScript syntax in layout-related fields
Enable web application firewall (WAF) rules that flag HTML and script tokens in addon update parameters

Monitoring Recommendations

Alert on authenticated sessions issuing POST requests containing script tokens to /apprain/developer/addons/update/canvasjs
Monitor administrator accounts for anomalous actions such as new user creation or privilege changes following addon configuration views
Track Content Security Policy (CSP) violation reports from the appRain CMF frontend to surface injected inline scripts

How to Mitigate CVE-2025-41052

Immediate Actions Required

Restrict access to /apprain/developer/addons/update/canvasjs to trusted administrative accounts only
Audit existing addon records for stored HTML or JavaScript content in the layouts and layouts_except fields and remove any unauthorized entries
Rotate session tokens and administrative credentials for accounts that interacted with the developer addons module during the exposure window

Patch Information

At the time of publication, no vendor patch is linked in the NVD record for appRain CMF 4.0.5. Monitor the INCIBE Security Notice on appRain CMF Vulnerabilities and the appRain project channels for a fixed release. Upgrade as soon as a corrected version becomes available.

Workarounds

Place the appRain CMF administrative interface behind a VPN or IP allowlist to reduce the attacker population
Deploy a WAF rule that strips or blocks <, >, and javascript: tokens in the data[Addon][layouts] and data[Addon][layouts_except] parameters
Enforce a strict Content Security Policy that disallows inline scripts in the CMF administrative views
Require multi-factor authentication for all accounts with access to the developer addons module

bash

# Example nginx rule to block script tokens in the vulnerable parameters
location /apprain/developer/addons/update/canvasjs {
    if ($request_body ~* "(data\[Addon\]\[layouts(_except)?\]=.*(<script|javascript:|onerror=|onload=))") {
        return 403;
    }
    proxy_pass http://apprain_backend;
}