# CVE-2026-54703: Markdown Preview Enhanced: Arbitrary File Write via updateMarkdown Command Without Path Validation

> An attacker with webview script execution can write arbitrary files via the updateMarkdown command, potentially leading to code execution or privilege escalation.

- **Severity:** Medium 5.8 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:N/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-82rc-7g3m-2c42

## What is CVE-2026-54703?

CVE-2026-54703 is a medium-severity path traversal 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 _crossnote.updateMarkdown command in Markdown Preview Enhanced accepts an arbitrary URI and attacker-controlled content, then passes them to vscode.workspace.fs.writeFile without validating that the target is the Markdown file represented by the current preview. JavaScript already executing in the preview webview can invoke this command through the extension message bridge and write any file permitted by the VS Code user's operating-system privileges, including user configuration, startup, source, and build files. This file-write vulnerability requires a separate webview JavaScript execution path, such as the independently tracked head.html injection and blind command-dispatch weaknesses. This issue is fixed in version 0.8.30.

Weakness: CWE-73 (External Control of File Name or Path)

## Which versions are affected by CVE-2026-54703?


## How do I fix CVE-2026-54703?

No fix has been published for CVE-2026-54703 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-54703 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54703 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54703 and fix it if it is affected.

What it is: CVE-2026-54703 is a medium-severity path traversal 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-2026-54703 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-2026-54703/ (Markdown: https://insights.sbomify.com/CVE-2026-54703/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54703
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54703
- OSV: https://osv.dev/vulnerability/CVE-2026-54703

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54703/
Summaries are generated and may contain mistakes; the official description above is the record.