Vulnerability · Published Jul 16, 2026 · Assigned by GitHub_M
CVE-2026-53597Prompty: Arbitrary code execution via JavaScript frontmatter in TypeScript loader
High 8.7
In plain English
A high-severity code injection in prompty from microsoft. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.0% (higher than 62% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | @prompty/core | 2.0.0-beta.3 | GHSA-c4gh-rv8h-q9vw |
Affected products (as reported)
Weakness: CWE-94 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N