CVE-2022-50940: Knap Advanced PHP Login XSS Vulnerability

CVE-2022-50940 Overview

CVE-2022-50940 is a persistent cross-site scripting (XSS) vulnerability in Knap Advanced PHP Login version 3.1.3. The vulnerability allows remote attackers to inject malicious script code through the name parameter. Once injected, the malicious scripts persist and execute in the users and activity log backend modules, potentially enabling session hijacking and persistent phishing attacks against administrators and other authenticated users.

Critical Impact

Attackers can persistently inject malicious JavaScript that executes whenever administrators view the users or activity log modules, enabling session hijacking and credential theft.

Affected Products

• Knap Advanced PHP Login version 3.1.3

Discovery Timeline

• 2026-02-01 - CVE-2022-50940 published to NVD
• 2026-02-03 - Last updated in NVD database

Technical Details for CVE-2022-50940

Vulnerability Analysis

This persistent XSS vulnerability (CWE-79) exists in the user registration or profile functionality of Knap Advanced PHP Login. The application fails to properly sanitize user-supplied input in the name parameter before storing it in the database and subsequently rendering it in administrative backend views.

The vulnerability is exploitable over the network and requires low privileges (an account on the system) along with user interaction (an administrator must view the affected module). The stored nature of this XSS makes it particularly dangerous as the malicious payload persists in the database and executes each time the compromised page is loaded.

Root Cause

The root cause is improper input validation and insufficient output encoding in the Knap Advanced PHP Login application. The name parameter accepts user input that is stored without sanitization and later displayed in the users and activity log backend modules without proper HTML entity encoding or contextual escaping, allowing embedded JavaScript to execute in the browser context of administrators viewing these modules.

Attack Vector

The attack vector is network-based, requiring an authenticated attacker to submit a crafted payload through the name parameter. The attack flow typically involves:

1. An attacker creates or modifies an account with a malicious script embedded in the name field
2. The payload is stored in the application database
3. When an administrator views the users module or activity log, the stored payload executes in their browser
4. The malicious script can steal session cookies, perform actions as the administrator, or redirect to phishing pages

The vulnerability can be exploited by injecting JavaScript payloads such as <script> tags or event handlers within the name parameter. When administrators navigate to the users or activity log modules, the unsanitized content is rendered, causing the browser to execute the injected scripts in the context of the authenticated session.

Detection Methods for CVE-2022-50940

Indicators of Compromise

• Unusual JavaScript tags or HTML elements stored in user name fields in the database
• Suspicious entries in activity logs containing script tags, event handlers (e.g., onerror, onload), or encoded payloads
• Administrator session anomalies or unauthorized administrative actions following log review activities
• Network traffic showing cookie exfiltration to external domains after accessing backend modules

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block common XSS payloads in form submissions
• Monitor database entries for the presence of HTML/JavaScript tags in user profile fields
• Review server logs for suspicious POST requests to user registration or profile update endpoints containing script tags
• Deploy Content Security Policy (CSP) headers to detect and report inline script execution violations

Monitoring Recommendations

• Enable detailed logging for user profile modifications and new registrations
• Configure alerting for CSP violation reports indicating attempted script injection
• Monitor administrator session activity for signs of session hijacking following access to user management modules
• Implement database integrity monitoring to detect unauthorized modifications to user records

How to Mitigate CVE-2022-50940

Immediate Actions Required

• Audit existing user records in the database for malicious payloads in the name field and sanitize any discovered entries
• Implement strict Content Security Policy (CSP) headers to prevent inline script execution
• Add Web Application Firewall rules to block XSS payloads targeting the name parameter
• Consider temporarily restricting access to administrative backend modules until patching is complete

Patch Information

No vendor patch has been confirmed at the time of this analysis. Organizations should monitor the VulnCheck Security Advisory and Vulnerability Lab #2307 for updates regarding official patches or security releases.

Workarounds

• Implement server-side input validation to strip or encode HTML/JavaScript from the name parameter before storage
• Apply output encoding (HTML entity encoding) when rendering user-supplied data in backend modules
• Deploy a Web Application Firewall with XSS protection rules enabled
• Implement HTTP-only and Secure flags on session cookies to reduce the impact of potential session hijacking

# Example: Apache mod_headers configuration for Content Security Policy
<IfModule mod_headers.c>
    Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'"
    Header set X-XSS-Protection "1; mode=block"
    Header set X-Content-Type-Options "nosniff"
</IfModule>