CVE-2026-53597: Microsoft Prompty

High severity, CVSS 8.7. EPSS: 1% chance of exploitation in the next 30 days.

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

• Microsoft Prompty: from 2.0.0-alpha.1, before 2.0.0-beta.3 (fixed in 2.0.0-beta.3)

Published 2026-07-16. Last modified 2026-07-18.