Affected: microsoft prompty

Prompty is a markdown file format (.prompty) for LLM prompts. Prior to 2.0.0-beta.2, Prompty loaders expanded ${file:...} references in .prompty frontmatter without enforcing that resolved paths stayed within the prompt directory or allowed roots, allowing an attacker-controlled prompt file to read local files through absolute paths, .. traversal, or symlink escapes. This issue is fixed in versions 2.0.0-beta.2.

Affected: PyPI: prompty, npm: @prompty/core, crates.io: prompty, NuGet: Prompty.Core

## Summary Prompty loaders expanded `${file:...}` references in `.prompty` frontmatter without enforcing that the resolved path stayed within an authorized directory. An attacker-controlled prompt file could use path traversal or an absolute path to cause the host application to read files accessible to the process.

## Affected packages - PyPI `prompty` versions `<= 2.0.0b1`; fixed in `2.0.0b2` - npm `@prompty/core` versions `<= 2.0.0-beta.1`; fixed in `2.0.0-beta.2` - crates.io `prompty` versions `<= 2.0.0-beta.1`; fixed in `2.0.0-beta.2` - NuGet `Prompty.Core` versions `<= 2.0.0-beta.1`; fixed in `2.0.0-beta.2`

## Impact Applications that load untrusted `.prompty` files, user-provided prompt paths, or prompt bundles from less-trusted locations could disclose local files available to the application process when expanded values are logged, returned, or otherwise exposed.

## Remediation Upgrade to the fixed runtime version for your ecosystem. The fix makes file references secure by default: `${file:...}` may only resolve within the directory tree containing the `.prompty` file. Host applications that need shared prompt assets outside that tree must explicitly provide allowed file roots through runtime load options. Absolute paths, `..` traversal, and symlink escapes outside allowed roots are rejected.

## Fix details The patched runtimes canonicalize file-reference targets and allowed roots before reading referenced files, reject targets outside the prompt directory by de…