CVE-2025-66400
mdast-util-to-hast has unsanitized class attribute
Impact
### Impact Multiple (unprefixed) classnames could be added in markdown source by using character references. This could make rendered user supplied markdown `code` elements appear like the rest of the page. The following markdown: ````markdown ```js xss ``` ```` Would create `<pre><code class="language-js xss"></code></pre>` If your page then applied `.xss` classes (or listeners in JS), those apply to this element. For more info see <https://github.com/ChALkeR/notes/blob/master/Improper-markup-sanitization.md#unsanitized-class-attribute> ### Patches The bug was patched. When using regular semver, run `npm install`. For exact ranges, make sure to use `13.2.1`. ### Workarounds Update. ### References * bug introduced in https://github.com/syntax-tree/mdast-util-to-hast/commit/6fc783ae6abdeb798fd5a68e7f3f21411dde7403 * bug fixed in https://github.com/syntax-tree/mdast-util-to-hast/commit/ab3a79570a1afbfa7efef5d4a0cd9b5caafbc5d7
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | mdast-util-to-hast | >= 13.0.0, < 13.2.1 | 13.2.1 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Unifiedjs | Mdast-Util-To-Hast | from 13.0.0 before 13.2.1 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/syntax-tree/mdast-util-to-hast/commit/6fc783ae6abdeb798fd5a68e7f3f21411dde7403
- https://github.com/syntax-tree/mdast-util-to-hast/commit/ab3a79570a1afbfa7efef5d4a0cd9b5caafbc5d7
- https://github.com/syntax-tree/mdast-util-to-hast/security/advisories/GHSA-4fh9-h7wg-q85m
- https://github.com/advisories/GHSA-4fh9-h7wg-q85m
- https://nvd.nist.gov/vuln/detail/CVE-2025-66400