High 7.2Published Oct 15, 2026

CVE-2026-104828HtmlUnit Neko: Mutation XSS (mXSS) in HTMLWriterFilter - TEXTAREA/TITLE entity decode without re-encode

Updated under an hour ago (2026-10-19 09:10 UTC)

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It affects htmlunit-neko. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.26%, higher than 17% of scored CVEs.

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Every CVE for htmlunit-neko

Exploited in the last 30 days

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.

CVSS: 7.2 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Weakness (CWE): CWE-79
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.26% (percentile 17)
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Oct 15, 2026
First seen by InfoSec Signals: Oct 15, 2026

Affected products

Affected products

HtmlUnit htmlunit-neko htmlunit:neko (from the name)	before 5.4.0	CNA record

References

https://github.com/HtmlUnit/htmlunit-neko/security/advisories/GHSA-39xg-prhf-8785x-refsource-confirm
https://github.com/HtmlUnit/htmlunit-neko/commit/c165891e0753aef3e05f5daa6250d3e8d4ada3c0x-refsource-misc
https://github.com/HtmlUnit/htmlunit-neko/releases/tag/5.4.0x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.