What’s Vulnerable › Vulnerabilities

CVE-2026-54701: Markdown Preview Enhanced: Stored XSS via Unsanitized `.crossnote/head.html` Injection in Webview

• Severity: medium (CVSS 6.9 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-14 · updated 2026-10-20
• Weakness: CWE-79

Description

Markdown Preview Enhanced is a Markdown preview extension for Visual Studio Code. Prior to 0.8.30, Markdown Preview Enhanced reads repository-controlled .crossnote/head.html content and passes it through resolvePathsInHeader before inserting it into the head of the preview webview document without removing executable content. Script-capable markup executes while the document loads, before the React application and DOMPurify initialize, and can access acquireVsCodeApi to send messages from the webview to the extension host. Opening a Markdown preview in a malicious repository is sufficient to trigger the injected content, and no additional click within the notification or preview is required. This issue is fixed in version 0.8.30.

Affected products

• shd101wyy vscode-markdown-preview-enhanced: before 0.8.30

References

• https://github.com/shd101wyy/crossnote/commit/8c55a2ba3365712a1caa4abeece0383bc2994d48
• https://github.com/shd101wyy/crossnote/pull/444
• https://github.com/shd101wyy/crossnote/releases/tag/0.9.31
• https://github.com/shd101wyy/vscode-markdown-preview-enhanced/commit/8bc848b6cbb42b9f35a0f95f7c3bf29b8302970e
• https://github.com/shd101wyy/vscode-markdown-preview-enhanced/pull/2323
• https://github.com/shd101wyy/vscode-markdown-preview-enhanced/releases/tag/0.8.30
• https://github.com/shd101wyy/vscode-markdown-preview-enhanced/security/advisories/GHSA-mcwg-4j78-qwv3
• https://github.com/shd101wyy/vscode-markdown-preview-enhanced/security/advisories/GHSA-mcwg-4j78-qwv3

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