md-editor-v3: XSS via fenced-code language rendering bypass — GHSA-3RM2-H79C-8QW6

Summary

### Summary `MdPreview` interpolates a fenced-code language into HTML attributes without escaping it. A crafted info string therefore executes JavaScript even when the shipped `XSSPlugin` is enabled. ### Details `useMarkdownIt()` (`packages/MdEditor/layouts/Content/composition/useMarkdownIt.ts:206`) registers a `highlight` callback whose final return inserts `language` into both `class="language-${language}"` and…

Timeline

Published by source

2026-09-18

Risk context

• Reported severity or threat level: medium.
• Reported CVSS score: 6.1 out of 10.
• Review exposure for the affected product or family: npm: md-editor-v3.

Product

npm: md-editor-v3

What to do

General, cautious steps (verify details in the official source):

• Review exposure and plan remediation based on risk and environment.
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-3RM2-H79C-8QW6

Source

GitHub

Vendor

GitHub

Published by source

2026-09-18

Last source activity

2026-09-18

Additional identifiers

CVE-2026-84992

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.