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

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-05 · updated 2026-10-26
Weakness: CWE-95

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.

Affected products

shd101wyy Markdown Preview Enhanced: before 0.8.28 — fixed in 0.8.28

How to fix

Upgrade to a fixed version: shd101wyy Markdown Preview Enhanced 0.8.28. Check the vendor advisory for mitigations.

References

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