CVE-2025-39505

Executive Summary

CVE-2025-39505 is a reflected Cross-Site Scripting (XSS) vulnerability in the Goodlayers Hotel WordPress plugin (gdlr-hotel), affecting versions up to and including 3.1.4. The vulnerability stems from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject arbitrary JavaScript into a reflected response. This can be exploited to steal session cookies, perform phishing attacks, or deface pages. The plugin is part of the WordPress ecosystem, and the vulnerability is not related to Apache or Nginx. No public exploit code or proof-of-concept is currently available, and the vendor has not released a patch.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository and third-party marketplaces. Users who installed the plugin from untrusted sources may be at higher risk of supply chain compromise. The lack of a patch increases the risk of unpatched installations being targeted.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Base Score: 7.1 (High)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (victim must click a crafted link)
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: Low

The vulnerability is rated High due to the low attack complexity and the ability to perform reflected XSS without authentication. However, user interaction is required, and the impact is limited to low-level confidentiality, integrity, and availability.

Deep Dive & Mechanics

The Goodlayers Hotel plugin fails to sanitize or escape user-supplied input before reflecting it in HTTP responses. An attacker can craft a malicious URL containing JavaScript payloads in parameters such as s, search, or other query strings. When a victim clicks the link, the payload executes in the context of the victim's browser, allowing the attacker to:

• Steal session cookies and impersonate the victim.
• Redirect the victim to malicious sites.
• Perform actions on behalf of the victim (e.g., changing settings).
• Inject keyloggers or other client-side malware.

The vulnerability is classified as Reflected XSS (CWE-79) and is triggered via HTTP GET requests. No authentication is required to exploit the flaw.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be in the plugin's core files, likely in gdlr-hotel/include/ or similar directories. The vulnerable pattern involves directly echoing user input without escaping:

// Vulnerable code (example)
echo '<div class="search-result">' . $_GET['s'] . '</div>';

A patched version would use WordPress's built-in escaping functions:

// Patched code (example)
echo '<div class="search-result">' . esc_html( $_GET['s'] ) . '</div>';

Without an official patch, users must manually apply input sanitization or disable the plugin.

Exploitation & Lab Setup

Red Team

Since no public exploit code is available, a proof-of-concept can be crafted:

<!-- Exploit URL example -->
http://target-site.com/?s=<script>alert('XSS')</script>

Steps:

1. Identify a vulnerable parameter (e.g., s, search, q).
2. Craft a URL with a JavaScript payload.
3. Deliver the link via phishing email or social engineering.
4. When the victim clicks, the payload executes.

Blue Team

Detection:

• Monitor web server logs for unusual query strings containing <script>, onerror, or javascript:.
• Use WAF rules to block reflected XSS patterns.
• Deploy CSP headers to mitigate impact.

Hunting:

• Search for gdlr-hotel plugin usage in the environment.
• Check for recent access logs with suspicious parameters.

Indicators of Compromise (IOCs)

• URL Patterns: ?s=<script>, ?search=javascript:, ?q=onerror=
• Log Entries: HTTP 200 responses with text/html containing unescaped <script> tags.
• File Hashes: (None available; plugin files may be modified by attackers)
• Network Traffic: Outbound connections to attacker-controlled domains from victim browsers.

Detection Engineering

YARA Rule

rule CVE_2025_39505_Reflected_XSS {
    meta:
        description = "Detects reflected XSS attempts against Goodlayers Hotel plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-39505"
    strings:
        $xss1 = /<script[^>]*>/i
        $xss2 = /onerror\s*=/i
        $xss3 = /javascript\s*:/i
        $plugin = "gdlr-hotel"
    condition:
        any of ($xss*) and $plugin
}

Sigma Rule

title: Reflected XSS Attempt Against Goodlayers Hotel Plugin
id: 8f3a2b1c-4d5e-6f7a-8b9c-0d1e2f3a4b5c
status: experimental
description: Detects reflected XSS attempts targeting the Goodlayers Hotel WordPress plugin
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-39505
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains:
            - '<script'
            - 'onerror='
            - 'javascript:'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in search queries (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-39505 Reflected XSS Attempt"; flow:to_server,established; content:"GET"; http_method; content:"gdlr-hotel"; http_uri; pcre:"/(<script|onerror=|javascript:)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Disable the Goodlayers Hotel plugin until a patch is available.
2. Short-term: Implement a Web Application Firewall (WAF) rule to block reflected XSS patterns.
3. Long-term: Monitor the vendor's website for updates. If no patch is released, consider replacing the plugin with an alternative.
4. Compensating Controls: Enforce Content Security Policy (CSP) headers to restrict script execution. Use X-XSS-Protection: 1; mode=block (deprecated but still useful).

Valters IT
DevSecOps & Cyber Threat Intelligence