CVE-2026-66683 in Custom CSS and JavaScript Plugin
Summary
by MITRE • 08/06/2026
Unauthenticated Sensitive Data Exposure in Custom CSS and JavaScript <= 2.0.16 versions.
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Analysis
by VulDB Data Team • 08/06/2026
This vulnerability represents a critical security flaw in the Custom CSS and JavaScript plugin for WordPress systems, affecting all versions up to and including 2.0.16. The issue stems from insufficient authentication checks within the plugin's file serving mechanism, allowing any unauthenticated user to access sensitive files that should only be available to authorized administrators. The vulnerability manifests when users attempt to access specific endpoints that serve custom CSS and JavaScript files, which contain configuration data, user credentials, or other confidential information that should remain protected.
The technical implementation flaw resides in the plugin's failure to properly validate user authentication status before serving sensitive content. When requests are made to the plugin's file delivery endpoints, the code does not verify whether the requesting user possesses adequate privileges to access the requested resources. This authentication bypass occurs due to missing or improperly implemented access control checks that should enforce administrative privileges for file retrieval operations. The vulnerability is classified as a weakness in authorization mechanisms and aligns with CWE-285, which addresses insufficient authorization in software systems.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can lead to complete system compromise when combined with other exploitation techniques. Attackers can leverage this flaw to extract sensitive configuration files that may contain database connection strings, API keys, or administrative credentials stored within the custom CSS and JavaScript files. The exposure creates a significant risk for WordPress installations where the plugin is in use, particularly in environments where multiple users have access to the site but should not be able to view administrative resources. This vulnerability directly supports the attack pattern described in the MITRE ATT&CK framework under T1213 - Data from Information Repositories, specifically targeting the extraction of sensitive data through unauthorized access.
Organizations using affected versions of this plugin face severe operational risks, including potential data breaches, regulatory compliance violations, and reputational damage. The vulnerability can be exploited remotely without requiring any prior authentication, making it particularly dangerous in public-facing web applications. Security professionals should immediately implement mitigations including updating to version 2.0.17 or later, which contains the necessary authentication checks, and reviewing access controls on affected systems. Additional protective measures include implementing proper network segmentation, monitoring for unauthorized file access attempts, and conducting comprehensive security audits of all installed WordPress plugins to identify similar vulnerabilities in the broader ecosystem.