CVE-2021-47906: BloofoxCMS Stored XSS Vulnerability

CVE-2021-47906 Overview

BloofoxCMS version 0.5.2.1 contains a stored cross-site scripting (XSS) vulnerability in the articles text parameter. This vulnerability allows authenticated attackers to inject malicious JavaScript payloads into the text field of articles, which are then executed when other users view the compromised content. The stored nature of this XSS vulnerability makes it particularly dangerous as the malicious payload persists in the application database and can affect multiple users over time.

Critical Impact

Authenticated attackers can steal session cookies, hijack user accounts, and potentially gain administrative access to the BloofoxCMS installation by exploiting the stored XSS in the articles text parameter.

Affected Products

• BloofoxCMS 0.5.2.1

Discovery Timeline

• 2026-01-23 - CVE CVE-2021-47906 published to NVD
• 2026-01-26 - Last updated in NVD database

Technical Details for CVE-2021-47906

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The root issue lies in insufficient input validation and output encoding within the BloofoxCMS article management functionality. When authenticated users create or edit articles, the content management system fails to properly sanitize the text parameter before storing it in the database and subsequently rendering it to other users.

The attack requires network access and authentication to the CMS, but only low privileges are needed to exploit it. User interaction is required as a victim must view the page containing the malicious payload. Successful exploitation can lead to confidentiality and integrity impacts on both the vulnerable system and potentially downstream systems.

Root Cause

The vulnerability stems from improper input validation and lack of output encoding in the article text handling functionality of BloofoxCMS. The application accepts user-supplied HTML and JavaScript content through the text parameter without adequate sanitization, allowing malicious scripts to be stored in the database. When the article is rendered for viewing, these scripts execute in the context of the victim's browser session.

Attack Vector

The attack is network-based and requires the attacker to have valid authentication credentials for the BloofoxCMS installation. The attacker crafts a malicious article containing JavaScript payloads in the text field. Common attack scenarios include:

The attacker creates an article with embedded JavaScript designed to capture session cookies and transmit them to an attacker-controlled server. When administrators or other authenticated users view the article, their session tokens are compromised, potentially allowing the attacker to hijack their sessions. Additional attack vectors include keylogging, phishing overlay injection, and cryptocurrency mining scripts.

Technical details and proof-of-concept information can be found in the Exploit-DB #49492 entry and the VulnCheck Advisory for BloofoxCMS.

Detection Methods for CVE-2021-47906

Indicators of Compromise

• Presence of <script> tags or JavaScript event handlers (such as onerror, onload, onclick) within article content in the database
• Unusual outbound network connections from client browsers when viewing CMS articles
• Unexpected cookie exfiltration attempts to external domains in web server or proxy logs
• Articles containing encoded or obfuscated JavaScript payloads

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block XSS patterns in HTTP requests targeting the article creation and editing endpoints
• Monitor database entries for the articles table for suspicious HTML/JavaScript content patterns
• Enable Content Security Policy (CSP) headers and monitor for policy violations in browser console logs
• Review access logs for unusual patterns of article creation or modification by low-privileged users

Monitoring Recommendations

• Configure alerts for CSP violation reports to detect attempted XSS exploitation
• Monitor for unusual session activity patterns that may indicate session hijacking following XSS attacks
• Implement audit logging for all article creation and modification events with full content capture
• Track outbound requests from the CMS application for potential data exfiltration indicators

How to Mitigate CVE-2021-47906

Immediate Actions Required

• Review all existing articles in the BloofoxCMS database for malicious JavaScript content and remove any suspicious payloads
• Implement strict Content Security Policy (CSP) headers to prevent inline script execution
• Consider temporarily restricting article creation/editing privileges to trusted administrators only
• Audit user accounts for any signs of compromise and force password resets if suspicious activity is detected

Patch Information

At the time of this advisory, users should check the GitHub BloofoxCMS Releases page for any available updates that address this vulnerability. The Bloofox Official Website may also contain security announcements and patched versions.

Workarounds

• Implement server-side input validation to strip or encode HTML and JavaScript from the article text parameter before storage
• Deploy a Web Application Firewall (WAF) with XSS protection rules in front of the BloofoxCMS installation
• Enable HTTP-only and Secure flags on all session cookies to reduce the impact of cookie theft via XSS
• Implement Content Security Policy headers with script-src 'self' to block inline scripts

# Example Apache configuration for Content Security Policy
# Add to .htaccess or Apache configuration
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self';"
Header set X-XSS-Protection "1; mode=block"
Header set X-Content-Type-Options "nosniff"