---
id: CVE-2026-104828
title: HtmlUnit Neko is an HtmlUnit adaptation of NekoHTML
summary: >-
  HtmlUnit Neko is an HtmlUnit adaptation of NekoHTML. Prior to 5.4.0,
  HTMLWriterFilter writes decoded TEXTAREA and TITLE character content without
  entity encoding because both elements are treated as special content. During a
  parse-and-se…
severity: high
cvss: 7.2
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N'
cwe:
  - CWE-79
vendor: HtmlUnit
product: htmlunit-neko
affected:
  - htmlunit-neko < 5.4.0
published: '2026-10-15'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T19:17:15.083'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-104828'
references:
  - url: >-
      https://github.com/HtmlUnit/htmlunit-neko/commit/c165891e0753aef3e05f5daa6250d3e8d4ada3c0
    label: security-advisories@github.com
  - url: 'https://github.com/HtmlUnit/htmlunit-neko/releases/tag/5.4.0'
    label: security-advisories@github.com
  - url: >-
      https://github.com/HtmlUnit/htmlunit-neko/security/advisories/GHSA-39xg-prhf-8785
    label: security-advisories@github.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-15T19:25:46.396Z'
---

## Overview

HtmlUnit Neko is an HtmlUnit adaptation of NekoHTML. Prior to 5.4.0, HTMLWriterFilter writes decoded TEXTAREA and TITLE character content without entity encoding because both elements are treated as special content. During a parse-and-serialize round trip, entity references inside these escapable raw-text elements are decoded by the parser and then emitted as raw markup by printCharacters(), changing the document's semantics. Applications that use htmlunit-neko in an HTML sanitizer, content filter, or other parse-transform-serialize pipeline can therefore turn attacker-controlled encoded text into executable markup when the output is rendered by a browser. This issue is fixed in version 5.4.0.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.