GHSA-w28w-gp39-m4p6

Prompty: Server-Side Template Injection to Remote Code Execution in the @prompty/core Nunjucks Renderer

Published

2026-07-24

Modified

2026-07-24

Sources

github-advisory

Summary

## Summary 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. ## Affected packages - npm `@prompty/core` versions `<= 0.1.4` - npm `@prompty/core` versions `<= 2.0.0-beta.4` ## Impact Applications that render untrusted, community-supplied, cloned, or LLM-generated `.prompty` files with the TypeScript runtime could allow attacker-controlled code execution with the privileges of the Node.js host process. ## Remediation Upgrade to `@prompty/core` `2.0.0-beta.5` or later. The patched renderer sanitizes render inputs to own-data-only values, rejects constructor/prototype member traversal, and disallows template function calls. Ordinary interpolation, conditionals, loops, and own nested data properties remain supported. ## Fix details The fix is merged in PR #404 and includes regression coverage for default Nunjucks rendering, explicit renderer usage, unsafe member lookups, and attempted template function calls.

Affected packages

Remediation: Upgrade to 0.1.5 or later.

References

• https://github.com/advisories/GHSA-w28w-gp39-m4p6