CVE-2023-6528: Slider Revolution WordPress RCE Vulnerability

CVE-2023-6528 Overview

CVE-2023-6528 is an insecure deserialization vulnerability affecting the Slider Revolution WordPress plugin before version 6.6.19. The vulnerability allows authenticated users with at least the Author role to unserialize arbitrary content when importing sliders, which can potentially lead to Remote Code Execution (RCE) on the affected WordPress installation.

Critical Impact

Authenticated attackers with Author privileges or higher can exploit this vulnerability to execute arbitrary code on the server, potentially leading to complete site compromise, data theft, or use of the server for further attacks.

Affected Products

• Themepunch Slider Revolution (WordPress plugin) versions before 6.6.19

Discovery Timeline

• 2024-01-08 - CVE-2023-6528 published to NVD
• 2025-06-03 - Last updated in NVD database

Technical Details for CVE-2023-6528

Vulnerability Analysis

This vulnerability stems from CWE-502 (Deserialization of Untrusted Data), a well-known class of security issues that occurs when an application deserializes data from untrusted sources without proper validation. In the context of the Slider Revolution plugin, the slider import functionality processes serialized PHP data without adequate sanitization, allowing authenticated users to inject malicious serialized objects.

PHP deserialization vulnerabilities are particularly dangerous in WordPress environments due to the presence of numerous "gadget chains" within WordPress core and popular plugins. When a malicious serialized object is processed, it can trigger magic methods like __wakeup() or __destruct() that lead to arbitrary code execution.

Root Cause

The root cause of CVE-2023-6528 lies in the slider import functionality within the Slider Revolution plugin. When users import slider configurations, the plugin processes serialized PHP data without implementing adequate safeguards against malicious payloads. The lack of proper validation or use of safe deserialization practices (such as using json_decode() instead of unserialize()) enables attackers to craft malicious serialized objects that execute arbitrary code upon deserialization.

Attack Vector

The attack requires network access and authentication with at least Author-level privileges on the WordPress installation. The attacker would need to:

1. Authenticate to the WordPress admin panel with Author or higher privileges
2. Access the Slider Revolution import functionality
3. Craft a malicious slider export file containing a serialized PHP object injection payload
4. Import the malicious file through the plugin interface
5. Upon deserialization, the malicious payload executes arbitrary code on the server

The vulnerability is exploited via the network attack vector and requires low privileges (authenticated user with Author role), making it accessible to a relatively wide range of potential attackers on multi-user WordPress installations. For detailed technical information, refer to the WPScan Vulnerability Details.

Detection Methods for CVE-2023-6528

Indicators of Compromise

• Unexpected slider imports in Slider Revolution plugin logs or activity
• Unusual file modifications in the WordPress installation directory, particularly in wp-content/uploads/ or plugin directories
• Suspicious PHP files created after slider import operations
• Anomalous outbound network connections from the web server
• WordPress database modifications indicating unauthorized access or backdoor installation

Detection Strategies

• Monitor WordPress admin activity logs for slider import operations, especially from Author-level accounts
• Implement file integrity monitoring to detect unauthorized file modifications in the WordPress installation
• Review web server access logs for POST requests to Slider Revolution import endpoints
• Utilize WordPress security plugins that detect PHP object injection attempts
• Deploy web application firewalls (WAF) with rules to detect serialized PHP payloads in form submissions

Monitoring Recommendations

• Enable detailed logging for the Slider Revolution plugin and WordPress admin actions
• Set up alerts for any slider import operations performed by users with Author-level privileges
• Monitor server resource usage for anomalies that might indicate code execution
• Implement network monitoring to detect unusual outbound connections from the web server

How to Mitigate CVE-2023-6528

Immediate Actions Required

• Update Slider Revolution plugin to version 6.6.19 or later immediately
• Audit user accounts with Author or higher privileges and remove unnecessary elevated access
• Review recent slider import activities for any suspicious operations
• Scan the WordPress installation for indicators of compromise or backdoors
• Consider temporarily disabling the slider import functionality if immediate patching is not possible

Patch Information

ThemePunch has addressed this vulnerability in Slider Revolution version 6.6.19. Administrators should update the plugin through the WordPress admin panel or by downloading the latest version from the official source. After updating, verify the plugin version by navigating to Plugins > Installed Plugins in the WordPress admin panel and confirming the version number displays 6.6.19 or higher.

Workarounds

• Restrict slider import functionality to only Administrator-level users by implementing role-based access controls
• Implement a web application firewall (WAF) to filter requests containing potentially malicious serialized PHP content
• Remove Author, Editor, or Contributor roles from untrusted users until the plugin can be updated
• Regularly audit user accounts and remove dormant or unnecessary accounts with elevated privileges
• Consider using WordPress security plugins that provide additional hardening and monitoring capabilities

# Verify current Slider Revolution version via WP-CLI
wp plugin list --name=revslider --fields=name,version

# Update Slider Revolution plugin to the latest version
wp plugin update revslider

# Audit user roles to identify accounts with Author or higher privileges
wp user list --role=author --fields=ID,user_login,user_email
wp user list --role=editor --fields=ID,user_login,user_email