---
id: CVE-2026-8445
aliases:
  - GHSA-3rcm-vjrc-p45j
title: JustHTML has a Sanitizer Bypass (in Markdown)
summary: JustHTML has a Sanitizer Bypass (in Markdown)
severity: medium
vendor: justhtml
product: justhtml
ecosystem: pip
affected:
  - justhtml < 1.12.0
patched:
  - justhtml 1.12.0
published: '2026-03-18'
updated: '2026-08-24'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-3rcm-vjrc-p45j'
references:
  - url: >-
      https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-3rcm-vjrc-p45j
  - url: 'https://github.com/EmilStenstrom/justhtml'
tags:
  - osv
  - pip
epss: 0.00381
epssPercentile: 0.31978
ingestedAt: '2026-08-24T19:25:43.962Z'
---

## Overview

## Summary

`to_markdown()` does not sufficiently escape text content that looks like HTML. As a result, untrusted input that is safe in `to_html()` can become raw HTML in Markdown output.

This is not specific to tokenizer raw-text states like `<title>`, `<noscript>`, or `<plaintext>`, although those states can trigger the behavior. The root cause is broader: Markdown text serialization leaves angle brackets unescaped in text nodes.

## Details

When converting a parsed document to Markdown, text nodes are escaped for a small set of Markdown metacharacters, but HTML-significant characters such as `<` and `>` are preserved. That means content parsed as text, including entity-decoded text or text produced by RCDATA/RAWTEXT-style parsing, can be emitted into Markdown as raw HTML.

Examples of affected input include:

- Text produced from entity-decoded input such as `&lt;script&gt;...&lt;/script&gt;`
- Text inside elements like `<title>`, `<textarea>`, `<noscript>` (when parsed as raw text), and `<plaintext>`

This is distinct from actual `<script>` or `<style>` elements in the DOM. Those are already dropped by default in `to_markdown()` unless `html_passthrough=True`.

## Proof of Concept

### General case

```python
from justhtml import JustHTML

doc = JustHTML("<p>&lt;img src=x onerror=alert(1)&gt;</p>", fragment=True)

print(doc.to_html())
print()
print(doc.to_markdown())

## Affected packages

- `justhtml < 1.12.0`

## Remediation

Upgrade to a patched release:

- `justhtml 1.12.0`