High severityNVD Advisory· Published Jul 16, 2026· Updated Jul 18, 2026
Prompty: Arbitrary code execution via JavaScript frontmatter in TypeScript loader
CVE-2026-53597
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 packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
@prompty/corenpm | >= 2.0.0-alpha.1, < 2.0.0-beta.3 | 2.0.0-beta.3 |
Affected products
2- Range: >=2.0.0-alpha.1 <2.0.0-beta.3
Patches
Vulnerability mechanics
References
4- github.com/advisories/GHSA-c4gh-rv8h-q9vwghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-53597ghsaADVISORY
- github.com/microsoft/prompty/commit/c27402da2487075be577f06aa79df627fb9d6853ghsax_refsource_MISCWEB
- github.com/microsoft/prompty/security/advisories/GHSA-c4gh-rv8h-q9vwghsax_refsource_CONFIRMWEB
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