# CVE-2026-50733: Markdown Preview Enhanced Arbitrary Code Execution via WaveDrom eval()

> Attackers can execute arbitrary code and write files by tricking users into previewing crafted Markdown with WaveDrom diagrams in Markdown Preview Enhanced.

- **Severity:** High 8.6 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 5 Jun 2026
- **Updated:** 5 Jun 2026
- **Also known as:** GHSA-j39p-jf99-v5w8

## What is CVE-2026-50733?

CVE-2026-50733 is a high-severity code injection vulnerability in shd101wyy Markdown Preview Enhanced, published on 5 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Markdown Preview Enhanced before 0.8.28 parses WaveDrom diagrams by evaluating untrusted markdown content with eval(), allowing arbitrary JavaScript execution. The flaw affects every render path - the live preview (window.eval) and presentation mode plus HTML export (the bundled WaveDrom.ProcessAll()/eva() helpers) - and can also be triggered through a <script type="WaveDrom"> element injected via raw HTML in markdown. When a victim previews or exports a crafted markdown document, an attacker can execute arbitrary code, leading to arbitrary file write. Fixed in 0.8.28 by parsing with JSON5.parse() and sanitizing WaveDrom data scripts to inert strict JSON.

Weakness: CWE-95 (Improper Neutralization of Directives in Dynamically Evaluated Code)

## Which versions are affected by CVE-2026-50733?


## How do I fix CVE-2026-50733?

No fix has been published for CVE-2026-50733 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-50733 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-50733 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-50733 and fix it if it is affected.

What it is: CVE-2026-50733 is a high-severity code injection vulnerability in shd101wyy Markdown Preview Enhanced, published on 5 Jun 2026. An attacker can exploit it over the internet without logging in, 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-2026-50733 exists.

Affected product: shd101wyy 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-2026-50733/ (Markdown: https://insights.sbomify.com/CVE-2026-50733/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-50733
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-50733
- OSV: https://osv.dev/vulnerability/CVE-2026-50733

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-50733/
Summaries are generated and may contain mistakes; the official description above is the record.