CVE-2026-8623
Received Received - Intake

Stored XSS in Dear Flipbook WordPress Plugin

Publication date: 2026-09-05

Last updated on: 2026-09-05

Assigner: Wordfence

Description
The Dear Flipbook – PDF Flipbook, 3D Flipbook, PDF embed, PDF viewer plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'post_content (class attribute of .dvcss element)' parameter in all versions up to, and including, 2.4.30 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The payload is embedded as a Base64-encoded JSON object in a CSS class name on a Custom HTML block; the frontend parseCSSElements() function decodes it client-side with atob() and JSON.parse() and renders the logo property as raw HTML, meaning no server-side or client-side sanitization intercepts the malicious script before DOM insertion.

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Meta Information

Published
2026-09-05
Last Modified
2026-09-05
Generated
2026-09-05
AI Q&A
2026-09-05
EPSS Evaluated
N/A
NVD
CVE-2026-8623
EUVD
EUVD-2026-71837

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
dear_flipbook pdf_flipbook to 2.4.30 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-79 The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

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Executive Summary

This is a Stored Cross-Site Scripting (XSS) vulnerability in the Dear Flipbook WordPress plugin. It allows authenticated attackers with contributor-level access or higher to inject malicious scripts into web pages via insufficient input sanitization in the 'post_content' parameter. The payload is embedded as a Base64-encoded JSON object in a CSS class name, which is later decoded and rendered as raw HTML on the frontend without proper sanitization.

Detection Guidance

This vulnerability requires checking WordPress sites using the Dear Flipbook plugin for malicious Base64-encoded JSON payloads in CSS class names of Custom HTML blocks. Inspect page sources for class attributes containing 'dvcss' with encoded data. Use WordPress admin tools to review Custom HTML blocks for suspicious content.

Impact Analysis

An attacker could steal user sessions, redirect users to malicious sites, or perform actions on their behalf. Since the payload executes when a user accesses an infected page, it poses risks to visitors of the WordPress site, including data theft or account compromise if the injected script is malicious.

Compliance Impact

This vulnerability could lead to non-compliance with GDPR (data protection) and HIPAA (health data privacy) by enabling unauthorized access to user data. If exploited, it may result in data breaches, triggering legal penalties, fines, or reputational damage due to failure to protect sensitive information.

Mitigation Strategies

Update the Dear Flipbook plugin to the latest version beyond 2.4.30. Remove or review Custom HTML blocks for malicious Base64-encoded payloads in CSS class names. Restrict contributor-level access to prevent exploitation. Monitor pages for unexpected script execution.

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