CVE-2026-31313: Feehi CMS Stored XSS Vulnerability

CVE-2026-31313 Overview

CVE-2026-31313 is an authenticated stored cross-site scripting (XSS) vulnerability affecting Feehi CMS version 2.1.1. The vulnerability exists in the content creation and editing module, where attackers with authenticated access can inject malicious web scripts or HTML payloads into the Content field. Once stored, these payloads execute in the browsers of other users who view the affected content, potentially leading to session hijacking, credential theft, or further attacks against the CMS infrastructure.

Critical Impact

Authenticated attackers can persistently inject malicious scripts that execute in victims' browsers, enabling session hijacking, phishing attacks, and unauthorized actions on behalf of legitimate users.

Affected Products

• Feehi CMS v2.1.1
• feehi:feehi_cms component

Discovery Timeline

• 2026-04-06 - CVE CVE-2026-31313 published to NVD
• 2026-04-09 - Last updated in NVD database

Technical Details for CVE-2026-31313

Vulnerability Analysis

This vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The flaw resides in the content management functionality of Feehi CMS, specifically within the creation and editing module where user-supplied content is accepted and stored without adequate sanitization.

When an authenticated user with content creation privileges submits a post or article, the Content field accepts HTML and JavaScript input that is stored directly in the database. Upon rendering this content to other users—including administrators—the malicious payload executes within their browser context. This stored (persistent) XSS variant is particularly dangerous because the payload persists across sessions and affects all users who access the compromised content.

The attack requires authentication but only low-level privileges, and successful exploitation depends on user interaction—specifically, a victim viewing the malicious content. The scope is changed, meaning the vulnerability can impact resources beyond the vulnerable component's security context.

Root Cause

The root cause of CVE-2026-31313 is insufficient input validation and output encoding in the Feehi CMS content management module. The application fails to properly sanitize user-supplied input before storing it in the database and does not adequately encode output when rendering content to end users. This allows HTML and JavaScript code to be interpreted and executed by the browser rather than being displayed as plain text.

Attack Vector

The attack vector is network-based, requiring an authenticated attacker to access the CMS administrative or content creation interface. The attacker crafts a malicious payload containing JavaScript code and injects it into the Content field during article creation or editing. The payload is stored in the CMS database and subsequently served to any user viewing the affected content.

A typical attack scenario involves an authenticated user with content authoring privileges inserting script tags or event handlers within the Content field. When administrators or other users view the content, the malicious script executes with the privileges of the viewing user's session, potentially allowing the attacker to steal session cookies, perform actions on behalf of the victim, or redirect users to malicious sites.

The vulnerability requires low attack complexity since no special conditions must be met beyond having authenticated access and a victim who views the injected content.

Detection Methods for CVE-2026-31313

Indicators of Compromise

• Unusual JavaScript code or <script> tags appearing in CMS content fields or database entries
• Content entries containing event handlers such as onerror, onload, onclick, or onmouseover with embedded JavaScript
• Unexpected external resource references or iframe injections within stored content
• User reports of suspicious browser behavior, pop-ups, or redirects when viewing CMS content

Detection Strategies

• Implement web application firewall (WAF) rules to detect XSS patterns in HTTP POST requests to content creation endpoints
• Deploy content security policy (CSP) headers to restrict script execution and report violations
• Conduct periodic database audits scanning for suspicious HTML and JavaScript patterns in content tables
• Enable browser-based XSS auditors and review security logs for blocked script execution attempts

Monitoring Recommendations

• Monitor access logs for unusual patterns in content creation and editing activity
• Establish baseline behavior for authenticated users and alert on anomalous content submission frequencies
• Track CSP violation reports to identify attempted XSS exploitation in real-time
• Review application error logs for encoding or rendering failures that may indicate injection attempts

How to Mitigate CVE-2026-31313

Immediate Actions Required

• Audit all existing content in Feehi CMS v2.1.1 for malicious script injections
• Implement strict input validation on the Content field, rejecting or sanitizing dangerous HTML and JavaScript
• Apply output encoding when rendering user-supplied content to prevent script execution
• Consider restricting content creation privileges to trusted users until a patch is available

Patch Information

As of the last NVD update on 2026-04-09, refer to the GitHub Issue #80 for the latest status on patches and vendor response. Users should monitor the Feehi CMS project for security updates and apply patches as soon as they become available. Additionally, review the Feehi Homepage for official announcements regarding security fixes.

Workarounds

• Implement a web application firewall (WAF) with XSS filtering rules to block malicious payloads before they reach the application
• Deploy Content Security Policy (CSP) headers with strict script-src directives to prevent inline script execution
• Use HTML sanitization libraries to strip dangerous tags and attributes from user-supplied content before storage
• Temporarily disable the WYSIWYG editor and restrict content input to plain text until the vulnerability is patched