GHSA-3rcm-vjrc-p45j
JustHTML has a Sanitizer Bypass (in Markdown)
Quick fix
GHSA-3rcm-vjrc-p45j — justhtml: upgrade to the fixed version with the command below.
pip install --upgrade 'justhtml>=1.12.0'Details
## 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 `<script>...</script>` - 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><img src=x onerror=alert(1)></p>", fragment=True)
print(doc.to_html()) print() print(doc.to_markdown())
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