CVE-2026-15758 in 3D FlipBook Plugin
Summary
by MITRE • 09/15/2026
The 3D FlipBook – PDF Embedder, PDF Flipbook Viewer, Flipbook Image Gallery plugin for WordPress is vulnerable to Sensitive Information Exposure in all versions up to, and including, 1.16.20 via the 'id' parameter. This makes it possible for unauthenticated attackers to extract sensitive data including the full metadata payload of password-protected flipbooks — including title, outline, props, and the serialized data blob containing the underlying PDF file's direct URL — bypassing WordPress post-password confidentiality. Flipbook post IDs can be pre-enumerated via the also-unauthenticated fb3d_send_posts AJAX action, requiring no prior knowledge to target specific flipbooks.
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability identified in the 3D FlipBook plugin for WordPress represents a critical failure in access control and data sanitization mechanisms within versions up to 1.16.20. This flaw allows unauthenticated attackers to bypass standard WordPress password protection protocols, which are designed to restrict content visibility to authorized users only. The core of the issue lies in how the plugin handles requests via its AJAX endpoints, specifically through the 'id' parameter used to retrieve flipbook data. Instead of enforcing strict authentication checks or validating user permissions before returning sensitive metadata, the application processes these requests openly, exposing internal structures and file paths that should remain hidden behind a login wall.
From a technical perspective, the vulnerability is exploited by leveraging the fb3d_send_posts AJAX action, which permits unauthenticated enumeration of flipbook post IDs. This capability effectively removes any barrier to entry for attackers seeking specific targets, as they do not need prior knowledge of valid identifiers to initiate an attack. Once a target ID is identified or guessed through sequential enumeration, the attacker can send crafted requests containing this 'id' parameter to extract detailed metadata payloads. These payloads include critical information such as the flipbook title, document outline, configuration props, and most significantly, serialized data blobs that contain direct URLs to the underlying PDF files. This exposure occurs regardless of whether the specific flipbook is configured with a password for public access control.
The operational impact of this vulnerability extends beyond simple privacy violations. By obtaining direct URLs to the source PDFs, attackers can download high-resolution copies of documents without ever needing to authenticate or guess passwords. This undermines the fundamental purpose of password-protected content in WordPress environments, where confidentiality is expected based on user credentials rather than obscurity. The exposure of metadata also aids further reconnaissance efforts, allowing adversaries to map out document structures and potentially identify other sensitive information embedded within the flipbooks. In enterprise or educational settings using this plugin for secure document sharing, such a flaw could lead to significant data breaches, intellectual property theft, and non-compliance with regulatory standards regarding data protection.
This issue aligns closely with CWE-200, which categorizes exposure of sensitive information to an unauthorized actor, as well as CWE-862, the lack of authorization for critical functionality. In terms of attack vectors, it corresponds to MITRE ATT&CK techniques related to Discovery and Collection, where adversaries gather information about systems or data before executing more intrusive actions. The ability to enumerate resources via AJAX endpoints without authentication is a common pattern in poorly secured WordPress plugins that prioritize convenience over security.
Mitigation strategies must focus on immediate remediation of the codebase alongside broader architectural improvements. Administrators should update the plugin to version 1.16.21 or later, where this specific flaw has been addressed by enforcing proper permission checks before returning metadata. For those unable to upgrade immediately, disabling the fb3d_send_posts AJAX action for unauthenticated users can prevent enumeration attacks. Additionally, implementing Web Application Firewall rules that monitor and restrict excessive requests to flipbook-related endpoints may help mitigate automated exploitation attempts. Long-term solutions involve auditing all third-party plugins for adherence to WordPress coding standards regarding authentication and authorization, ensuring that sensitive data is never exposed through API responses without rigorous validation of user privileges.