CVE-2026-78566: WordPress Shuffle Theme RCE Vulnerability

CVE-2026-78566 Overview

CVE-2026-78566 is a Local File Inclusion (LFI) vulnerability affecting the Shuffle theme for WordPress in all versions up to and including 1.8. Unauthenticated attackers can include and execute arbitrary files on the server, resulting in execution of PHP code contained in those files. The flaw is classified under CWE-98 (Improper Control of Filename for Include/Require Statement in PHP Program).

The vulnerability enables access control bypass, disclosure of sensitive data, and remote code execution when combined with the ability to upload files of otherwise "safe" types such as images. WordPress sites running the Shuffle theme are exposed until the plugin is removed or replaced.

Critical Impact
Unauthenticated remote attackers can execute arbitrary PHP code on servers running the Shuffle WordPress theme, leading to full site compromise.

Affected Products

Shuffle theme for WordPress — all versions up to and including 1.8
WordPress installations that expose the vulnerable theme's PHP endpoints
Hosting environments allowing file uploads that could be chained with the LFI

Discovery Timeline

2026-08-25 - CVE-2026-78566 published to NVD
2026-08-26 - Last updated in NVD database

Technical Details for CVE-2026-78566

Vulnerability Analysis

The Shuffle theme processes user-controlled input inside a PHP include or require statement without sufficient validation or sanitization. Attackers supply a crafted parameter that references an arbitrary file path, and the theme evaluates the referenced file as PHP source code.

Because the vulnerable code path does not require authentication, any anonymous visitor can reach it directly over HTTP. Successful exploitation yields code execution in the context of the web server process, exposing the WordPress database credentials in wp-config.php and any other files readable by PHP.

When an attacker can upload files, even benign types like PNG or JPG, the LFI becomes a full remote code execution primitive. The uploaded file's PHP payload executes when included through the vulnerable parameter.

Root Cause

The root cause is improper control of a filename parameter used in a PHP file inclusion statement, categorized as CWE-98. The theme trusts request-supplied input to construct include paths without validating that the resolved path stays inside an allow-listed directory.

Attack Vector

Exploitation occurs over the network via crafted HTTP requests to the vulnerable theme endpoint. No authentication or user interaction is required. Attack complexity is elevated because the attacker must know or guess the parameter name and satisfy path resolution constraints on the target host.

Detailed vulnerability write-ups are available in the Patchstack Shuffle Theme Vulnerability advisory and the Wordfence Vulnerability Report.

Detection Methods for CVE-2026-78566

Indicators of Compromise

HTTP requests to Shuffle theme PHP files containing path traversal sequences such as ../ or absolute paths like /etc/passwd
Access log entries referencing wp-content/themes/shuffle/ with unexpected query parameters pointing to file paths
New or modified PHP files inside wp-content/uploads/ or theme directories
Outbound network connections from the web server process to unfamiliar hosts following suspicious requests

Detection Strategies

Inspect web server access logs for requests targeting the Shuffle theme with parameters that resolve to filesystem paths
Deploy web application firewall rules that block path traversal patterns and PHP wrapper schemes such as php://filter
Monitor file integrity across wp-content/ for unauthorized additions or modifications
Correlate PHP process activity with unexpected child processes such as sh, bash, or python

Monitoring Recommendations

Forward WordPress, PHP-FPM, and web server logs to a centralized analytics platform for retention and query
Alert on 200-status responses to requests containing filesystem path characters against theme resources
Baseline outbound traffic from the web tier and alert on new destinations after theme endpoint access

How to Mitigate CVE-2026-78566

Immediate Actions Required

Deactivate and remove the Shuffle theme from all WordPress installations until a fixed version is confirmed available
Rotate WordPress administrator passwords, database credentials, and any API keys stored in wp-config.php
Review wp-content/uploads/ and theme directories for webshells or unfamiliar PHP files and remove them
Audit user accounts for unauthorized administrators created during the exposure window

Patch Information

No vendor patch is referenced in the advisory data for versions above 1.8 at the time of publication. Monitor the Patchstack advisory and Wordfence report for fix availability, and replace the theme with a maintained alternative if no patch is released.

Workarounds

Block requests to Shuffle theme PHP files at the web application firewall or reverse proxy
Set allow_url_include=Off and restrict open_basedir in php.ini to limit include paths
Disable PHP execution in the wp-content/uploads/ directory using web server configuration
Restrict file upload MIME types and validate uploaded content server-side

bash

# Nginx: disable PHP execution in uploads and block Shuffle theme access
location ~* /wp-content/uploads/.*\.php$ {
    deny all;
    return 403;
}

location ~* /wp-content/themes/shuffle/ {
    deny all;
    return 403;
}

# php.ini hardening
# allow_url_include = Off
# open_basedir = /var/www/html:/tmp