CVE-2020-37227: HS Brand Logo Slider RCE Vulnerability

CVE-2020-37227 Overview

CVE-2020-37227 is an unrestricted file upload vulnerability in the HS Brand Logo Slider WordPress plugin version 2.1. The plugin relies on client-side validation to restrict logo image uploads through the admin interface. Authenticated attackers can intercept the upload request, rename a malicious payload to a PHP extension, and bypass this control. Successful exploitation grants remote code execution on the underlying web server. The flaw is classified as CWE-434: Unrestricted Upload of File with Dangerous Type.

Critical Impact
Authenticated attackers can upload .php files to the WordPress server through the logoupload parameter and execute arbitrary code in the web server context.

Affected Products

HS Brand Logo Slider WordPress plugin version 2.1
WordPress installations with the plugin enabled
Developed by Helios Solutions

Discovery Timeline

2026-05-16 - CVE-2020-37227 published to NVD
2026-05-18 - Last updated in NVD database

Technical Details for CVE-2020-37227

Vulnerability Analysis

The HS Brand Logo Slider 2.1 plugin exposes a logo upload feature in the WordPress admin interface. The plugin enforces file extension restrictions only in browser-side JavaScript. Server-side validation of the uploaded file type, MIME type, and extension is absent.

An attacker authenticated to the WordPress admin panel can submit a POST request to the upload endpoint with the logoupload parameter. Using an intercepting proxy, the attacker modifies the filename from a permitted image extension to .php after the client-side check executes. The plugin writes the file to a web-accessible directory within wp-content, allowing direct execution by requesting the resulting URL.

Root Cause

The root cause is missing server-side validation of uploaded file types. The plugin trusts the file extension presented in the multipart upload request. No allowlist of permitted MIME types, magic byte inspection, or rename-on-upload logic exists to neutralize executable extensions.

Attack Vector

Exploitation requires an authenticated session with privileges to access the plugin's upload functionality. The attacker proxies the upload request through a tool such as Burp Suite. The attacker selects a benign .jpg or .png file to satisfy the client-side filter, then rewrites the filename and content to a PHP web shell before forwarding the request. The server stores the file and returns a path that the attacker requests to execute arbitrary commands. Technical details are documented in Exploit-DB #48913 and the VulnCheck advisory.

Detection Methods for CVE-2020-37227

Indicators of Compromise

PHP files with non-standard names located in wp-content/uploads/ or plugin-specific upload directories
HTTP POST requests to admin endpoints containing the logoupload parameter with filenames ending in .php, .phtml, or .phar
Unexpected outbound connections from the web server process following admin file uploads
New scheduled tasks, cron entries, or modified WordPress option values created after a logo upload event

Detection Strategies

Monitor web server logs for POST requests to plugin upload handlers immediately followed by GET requests to newly created files in upload directories
Inspect uploaded files for PHP tags (<?php, <?=) or shell function calls regardless of extension
Alert on web server worker processes spawning shells such as /bin/sh, bash, cmd.exe, or powershell.exe
Deploy file integrity monitoring on wp-content/ directories to flag new executable scripts

Monitoring Recommendations

Centralize WordPress access logs and audit them for anomalous administrative upload activity
Track authenticated admin sessions and correlate file write events with the originating user account
Establish baseline upload patterns and alert on deviations such as unusual file sizes or extensions

How to Mitigate CVE-2020-37227

Immediate Actions Required

Disable and remove the HS Brand Logo Slider 2.1 plugin until a fixed version is verified
Audit wp-content/uploads/ and plugin upload directories for unauthorized .php files and remove any web shells
Rotate WordPress administrative credentials and review user accounts for unauthorized additions
Review web server access logs for prior exploitation evidence dating back to plugin installation

Patch Information

No vendor patch information is referenced in the CVE record. Consult the WordPress plugin page and the Helios Solutions site for plugin updates. Until a verified fix is available, uninstalling the plugin is the recommended action.

Workarounds

Restrict access to the WordPress admin interface using IP allowlists or VPN-only access
Configure the web server to deny PHP execution within upload directories using .htaccess rules or equivalent Nginx location blocks
Deploy a web application firewall rule that blocks multipart requests where the filename ends in executable extensions
Enforce least privilege on WordPress accounts and limit plugin management to a minimal set of administrators

bash

# Apache: deny PHP execution in WordPress uploads directory
# Place in wp-content/uploads/.htaccess
<FilesMatch "\.(php|phtml|phar|php[0-9]?)$">
    Require all denied
</FilesMatch>

# Nginx equivalent: add to server block
location ~* /wp-content/uploads/.*\.(php|phtml|phar)$ {
    deny all;
    return 403;
}