Description
Prompty is a markdown file format (.prompty) for LLM prompts. Prior to 0.1.5 and 2.0.0-beta.5, the TypeScript Nunjucks renderer evaluated untrusted .prompty template bodies with unrestricted JavaScript member access. An attacker-controlled template could traverse constructor and prototype properties to execute JavaScript in the host Node.js process. This issue is fixed in versions 0.1.5 and 2.0.0-beta.5.
References6
- github.com/microsoft/prompty/commit/e4a0ebf49e3a78d5d7796c8480b…
- github.com/microsoft/prompty/commit/f5c57c94a0990cca79d095c3daa…
- github.com/microsoft/prompty/pull/404
- github.com/microsoft/prompty/pull/405
- github.com/microsoft/prompty/security/advisories/GHSA-w28w-gp39…
- github.com/microsoft/prompty/tree/typescript/2.0.0-beta.5
Metrics
- CVSS 3.1
-
10.0
CRITICAL
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H - EPSS — exploit probability
- 2% percentile: 79 · as of 12 November 2026
- CWE
- CWE-94CWE-1336
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.