CVE-2025-41054: Apprain CMF Stored XSS Vulnerability

CVE-2025-41054 Overview

CVE-2025-41054 is a stored cross-site scripting (XSS) vulnerability in appRain CMF version 4.0.5. The flaw resides in the /apprain/developer/addons/update/cycle endpoint, which fails to properly validate user input passed through the data[Addon][layouts] and data[Addon][layouts_except] parameters. An authenticated attacker can inject JavaScript payloads that persist in the application and execute in the browsers of other users who visit the affected pages. The vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation.

Critical Impact
An authenticated attacker can inject persistent JavaScript that executes in the sessions of other users, enabling session theft, credential harvesting, and administrative account compromise.

Affected Products

appRain CMF 4.0.5
Deployments exposing the developer addons update interface
Instances allowing low-privilege authenticated user accounts

Discovery Timeline

2025-09-04 - CVE-2025-41054 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-41054

Vulnerability Analysis

The vulnerability is a stored XSS flaw affecting the addon update workflow in appRain CMF. The application accepts user-supplied values for the data[Addon][layouts] and data[Addon][layouts_except] parameters without applying output encoding or input sanitization. Payloads submitted through these fields are persisted server-side and rendered as raw HTML when subsequent users load the addon management views.

Exploitation requires prior authentication, which limits opportunistic attacks but does not prevent abuse by users with legitimate low-privileged accounts. Once a payload is stored, any administrator or reviewer visiting the affected page triggers script execution in their authenticated session context.

Root Cause

The root cause is missing input validation and output encoding on the data[Addon][layouts] and data[Addon][layouts_except] request parameters processed by the /apprain/developer/addons/update/cycle endpoint. Values are stored in the addon configuration and later reflected into HTML responses without contextual escaping, allowing arbitrary <script> payloads to persist and execute.

Attack Vector

The attack vector is network-based and requires an authenticated session on the target appRain CMF instance. An attacker submits a crafted POST request to /apprain/developer/addons/update/cycle containing a malicious payload in either the data[Addon][layouts] or data[Addon][layouts_except] parameter. When another authenticated user, typically an administrator, loads the affected addon view, the injected script runs in their browser and can exfiltrate session tokens, perform actions on their behalf, or pivot to further compromise. Technical details are documented in the INCIBE Notice on Multiple Vulnerabilities in appRain CMF.

Detection Methods for CVE-2025-41054

Indicators of Compromise

HTTP POST requests to /apprain/developer/addons/update/cycle containing HTML tags, JavaScript event handlers, or encoded script fragments in the data[Addon][layouts] or data[Addon][layouts_except] parameters.
Unexpected outbound requests from administrator browsers to attacker-controlled domains shortly after loading addon management pages.
Addon configuration records in the database containing <script>, onerror=, onload=, or javascript: strings in layout fields.

Detection Strategies

Inspect web server and application logs for parameter values in addon update requests that contain script tags, encoded angle brackets, or common XSS polyglots.
Deploy Content Security Policy (CSP) reporting to surface script executions from unexpected sources in the appRain CMF administrative interface.
Perform periodic database audits of the addon configuration tables for stored HTML or JavaScript content in layouts and layouts_except fields.

Monitoring Recommendations

Alert on anomalous access patterns to /apprain/developer/addons/* endpoints from non-developer accounts.
Correlate authenticated user activity with subsequent administrator session anomalies, such as new API tokens or password changes.
Monitor browser telemetry from administrative workstations for script execution originating from the appRain CMF domain that contacts external hosts.

How to Mitigate CVE-2025-41054

Immediate Actions Required

Restrict access to the /apprain/developer/addons/update/cycle endpoint to trusted developer accounts using network-level or application-level controls.
Audit existing addon configuration records for stored HTML or JavaScript content and remove any malicious payloads.
Rotate session tokens and administrator credentials if evidence of stored XSS payloads is discovered.

Patch Information

No vendor patch or fixed version is referenced in the available advisory data. Administrators should monitor the INCIBE Notice on Multiple Vulnerabilities in appRain CMF and the appRain project for an official update addressing CVE-2025-41054.

Workarounds

Place the appRain CMF administrative interface behind a VPN or IP allowlist to reduce the pool of accounts that can submit addon updates.
Deploy a Web Application Firewall (WAF) rule blocking requests to /apprain/developer/addons/update/cycle where data[Addon][layouts] or data[Addon][layouts_except] contain HTML tags or JavaScript keywords.
Enforce a strict Content Security Policy that disallows inline scripts and restricts script sources to trusted origins.
Review and limit developer role assignments so that only vetted personnel can invoke addon update functionality.

bash

# Example WAF rule (ModSecurity) blocking script payloads in addon layout parameters
SecRule REQUEST_URI "@contains /apprain/developer/addons/update/cycle" \
    "phase:2,deny,status:403,id:1004105401,\
    chain,msg:'Potential XSS in appRain addon layouts (CVE-2025-41054)'"
    SecRule ARGS:'data[Addon][layouts]|ARGS:data[Addon][layouts_except]' \
        "@rx (?i)(<script|onerror=|onload=|javascript:)"