# CVE-2026-54702: Markdown Preview Enhanced: Blind Command Dispatch via Unvalidated Webview Message Handler

> Attackers with webview script execution can invoke privileged extension commands to execute code or modify files due to missing input validation in the message handler.

- **Severity:** High 7.3 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/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:** 15 Oct 2026
- **Also known as:** GHSA-83c6-hcjv-pvmg

## What is CVE-2026-54702?

CVE-2026-54702 is a high-severity code injection 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, the webview message handler in src/preview-provider.ts accepts an attacker-controlled command value and attacker-controlled args, constructs a command in the _crossnote namespace, and invokes vscode.commands.executeCommand without an allowlist or type validation. JavaScript already executing in the preview webview can use this bridge to invoke privileged extension commands, including file modification, code-chunk execution, export-tool execution, and arbitrary URL opening, with attacker-selected arguments. Exploitation requires a separate webview JavaScript execution path, such as the independently tracked .crossnote/head.html injection, but no further authorization check protects the extension-host command boundary. This issue is fixed in version 0.8.30.

Weakness: CWE-749 (Exposed Dangerous Method or Function)

## Which versions are affected by CVE-2026-54702?


## How do I fix CVE-2026-54702?

No fix has been published for CVE-2026-54702 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-54702 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54702 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54702 and fix it if it is affected.

What it is: CVE-2026-54702 is a high-severity code injection 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-2026-54702 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-2026-54702/ (Markdown: https://insights.sbomify.com/CVE-2026-54702/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54702
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54702
- OSV: https://osv.dev/vulnerability/CVE-2026-54702

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-54702/
Summaries are generated and may contain mistakes; the official description above is the record.