CVE-2026-31354: Feehi CMS Stored XSS Vulnerability

CVE-2026-31354 Overview

Multiple authenticated stored cross-site scripting (XSS) vulnerabilities have been identified in the Permissions module of Feehi CMS version 2.1.1. These vulnerabilities allow authenticated attackers to execute arbitrary web scripts or HTML by injecting a crafted payload into the Group, Category, or Description parameters within the administrative interface.

Critical Impact

Authenticated attackers can inject persistent malicious scripts that execute in the context of other users' browsers, potentially leading to session hijacking, administrative account compromise, or further attacks against CMS users.

Affected Products

• Feehi CMS v2.1.1
• Permissions module administrative interface
• Group, Category, and Description parameter input fields

Discovery Timeline

• 2026-04-06 - CVE-2026-31354 published to NVD
• 2026-04-09 - Last updated in NVD database

Technical Details for CVE-2026-31354

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting (XSS). The stored XSS variant present in Feehi CMS is particularly dangerous because malicious payloads are permanently stored on the target server within the Permissions module database.

When an administrator or user with appropriate privileges accesses the affected Permissions module, the stored malicious script is retrieved from the database and rendered in the browser without proper sanitization. This allows the attacker's JavaScript code to execute within the security context of the victim's session.

The attack requires low privileges to execute, as the attacker needs authenticated access to the CMS to inject payloads. However, the impact extends beyond the attacker's privilege level since the malicious scripts execute in the context of any user viewing the affected content, including administrators.

Root Cause

The root cause of this vulnerability is insufficient input validation and output encoding in the Permissions module of Feehi CMS. The application fails to properly sanitize user-supplied input in the Group, Category, and Description parameters before storing the data in the database. Additionally, the application does not implement proper output encoding when rendering this data back to users, allowing raw HTML and JavaScript to be executed in the browser context.

Attack Vector

The attack is carried out over the network and requires the attacker to have authenticated access to the Feehi CMS administrative interface. The exploitation flow involves:

1. An authenticated attacker navigates to the Permissions module within the CMS
2. The attacker crafts a malicious payload containing JavaScript code (e.g., <script> tags or event handlers)
3. The payload is submitted through the Group, Category, or Description input fields
4. The malicious content is stored persistently in the application database
5. When another user (including administrators) views the affected permission entries, the stored script executes in their browser

Since user interaction is required for the script to execute (viewing the affected page), this vulnerability relies on victims accessing the compromised administrative pages. The scope is changed as the vulnerability affects users other than the authenticated attacker who injected the payload.

Detection Methods for CVE-2026-31354

Indicators of Compromise

• Unusual script tags or JavaScript event handlers stored in Permission module database entries
• Unexpected HTML entities in Group, Category, or Description fields that may indicate encoding bypass attempts
• Administrative logs showing permission entries containing suspicious characters like <, >, ", or ' followed by script keywords

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block XSS payloads in POST requests to the Permissions module endpoints
• Monitor application logs for requests containing script tags or common XSS patterns in form parameters
• Conduct regular database audits to identify stored content containing potentially malicious script elements

Monitoring Recommendations

• Enable verbose logging for all administrative actions within Feehi CMS
• Configure alerts for any database changes to permission-related tables that contain HTML or JavaScript syntax
• Monitor for unusual session behavior that may indicate session hijacking following XSS exploitation

How to Mitigate CVE-2026-31354

Immediate Actions Required

• Review and audit existing Permission module entries for any stored malicious payloads
• Restrict access to the Permissions module to only essential administrative personnel
• Implement Content Security Policy (CSP) headers to mitigate the impact of any stored XSS payloads
• Consider temporarily disabling the affected input fields until a patch is available

Patch Information

At the time of publication, no official patch has been released by the vendor. Users should monitor the GitHub CMS Project for security updates and the GitHub Issue #85 Discussion for any developments regarding this vulnerability. It is recommended to upgrade to a patched version as soon as one becomes available.

Workarounds

• Implement server-side input validation to strip or encode HTML special characters from Group, Category, and Description fields
• Apply output encoding (HTML entity encoding) when rendering Permission module data in the administrative interface
• Deploy a Web Application Firewall with XSS detection rules to filter malicious payloads before they reach the application

# Example Apache CSP header configuration to mitigate XSS impact
<IfModule mod_headers.c>
    Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; object-src 'none';"
</IfModule>