# OWASP Java HTML Sanitizer is vulnerable to XSS via noscript tag and improper style tag sanitization

Advisory record · `GHSA-g9gq-3pfx-2gw2`

- **Identifiers:** `GHSA-g9gq-3pfx-2gw2` · `CVE-2025-66021`
- **State:** Confirmed
- **Severity:** CVSS 8.6 High
- **Critical:** No
- **Weakness (CWE):** [CWE-79](https://cwe.mitre.org/data/definitions/79.html)
- **Tags:** [Cross-site scripting (XSS)](https://agentprime.io/advisories/tag/xss.md)
- **Published:** 25 Nov 2025
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 25 Nov 2025, 22:10 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `com.googlecode.owasp-java-html-sanitizer:owasp-java-html-sanitizer` (Maven): affected `>=20240325.1, <20260101.1`; fixed in `20260101.1`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> The Maven package com.googlecode.owasp-java-html-sanitizer:owasp-java-html-sanitizer versions 20240325.1 up to but not including 20260101.1 is affected. The issue arises only when a policy built with HtmlPolicyBuilder allows both noscript and style tags, with allowTextIn set for style, and the sanitized output is then rendered in a browser, which can let crafted script run. Upgrade to version 20260101.1, which is the listed fix. The source gives few details about the exact conditions beyond this.

Written 2 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 8.6 High, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0029, the 21st percentile, on 12 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:17 UTC: First seen by agentprime
- 31 Oct 2026, 14:17 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-g9gq-3pfx-2gw2)

## Sources

- [GitHub Advisory Database: GHSA-g9gq-3pfx-2gw2](https://github.com/advisories/GHSA-g9gq-3pfx-2gw2)
- [OSV: GHSA-g9gq-3pfx-2gw2](https://osv.dev/vulnerability/GHSA-g9gq-3pfx-2gw2)
- <https://github.com/OWASP/java-html-sanitizer/security/advisories/GHSA-g9gq-3pfx-2gw2>
- <https://nvd.nist.gov/vuln/detail/CVE-2025-66021>
- <https://github.com/OWASP/java-html-sanitizer/issues/363>
- <https://github.com/OWASP/java-html-sanitizer/commit/4149cf02ba84db13e8e9d7ee1b01b3f47238e072>
- <https://github.com/OWASP/java-html-sanitizer/commit/b98cdf1cd5e156a6259b01aa8cdc7372c6efde1e>
- <https://github.com/OWASP/java-html-sanitizer/commit/d6e0463ed3b48777ecd187913ffdbe767508ff45>
- <https://github.com/OWASP/java-html-sanitizer>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-g9gq-3pfx-2gw2>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-g9gq-3pfx-2gw2/>. Everything for agents: <https://agentprime.io/llms.txt>.