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OpenAdvisories
High · 8.7 CVE-2026-53597 EUVD-2026-44939GHSA-c4gh-rv8h-q9vw

Prompty: Arbitrary code execution via JavaScript frontmatter in TypeScript loader

Published Jul 16, 2026 · Updated Jul 18, 2026 · Assigned by GitHub_M

Description

Prompty is a markdown file format (.prompty) for LLM prompts. From 2.0.0-alpha.1 until 2.0.0-beta.3, the @prompty/core TypeScript loader in runtime/typescript/packages/core/src/core/loader.ts used gray-matter without overriding executable js and javascript frontmatter engines, allowing an attacker-controlled .prompty file with ---js frontmatter to execute arbitrary JavaScript during prompt loading. This issue is fixed in version 2.0.0-beta.3.

Affected products

VendorProductAffectedFixed
microsoft prompty >= 2.0.0-alpha.1, < 2.0.0-beta.3 —

Affected packages

EcosystemPackageAffectedFixedRecord
npm @prompty/core >= 2.0.0-alpha.1, < 2.0.0-beta.3 2.0.0-beta.3 GHSA-c4gh-rv8h-q9vw

References