HtmlUnit Neko: Mutation XSS (mXSS) in HTMLWriterFilter - TEXTAREA/TITLE entity decode without re-encode
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.
CVE-2026-104828
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-104828
htmlunit-neko
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "HtmlUnit",
"product": "htmlunit-neko",
"versions": [
{
"status": "affected",
"version": "< 5.4.0"
}
]
}
]- Related CVEs
- CVE-2026-104828
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #44990 · Revision 1
- Added to Heist Feed
- Publisher date