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

> Attackers can execute arbitrary scripts in VS Code by injecting malicious HTML into repository files, potentially compromising the extension host.

- **Severity:** Medium 6.9 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 14 Oct 2026
- **Updated:** 20 Oct 2026
- **Also known as:** GHSA-mcwg-4j78-qwv3

## What is CVE-2026-54701?

CVE-2026-54701 is a medium-severity cross-site scripting vulnerability in shd101wyy vscode-markdown-preview-enhanced, published on 14 Oct 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-54701?


## How do I fix CVE-2026-54701?

No fix has been published for CVE-2026-54701 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-54701 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54701 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54701 and fix it if it is affected.

What it is: CVE-2026-54701 is a medium-severity cross-site scripting vulnerability in shd101wyy vscode-markdown-preview-enhanced, published on 14 Oct 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54701 exists.

Affected product: shd101wyy vscode-markdown-preview-enhanced. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-54701/ (Markdown: https://insights.sbomify.com/CVE-2026-54701/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54701
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54701
- OSV: https://osv.dev/vulnerability/CVE-2026-54701

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54701/
Summaries are generated and may contain mistakes; the official description above is the record.