{"id":"GHSA-c4gh-rv8h-q9vw","summary":"Prompty: Arbitrary code execution via JavaScript frontmatter in TypeScript loader","details":"## Summary\nThe TypeScript Prompty loader used `gray-matter` without overriding executable frontmatter engines. `gray-matter` supports JavaScript frontmatter blocks such as `---js` and evaluates them while parsing. An attacker-controlled `.prompty` file could therefore execute arbitrary JavaScript during prompt loading.\n\n## Affected package\n- npm `@prompty/core` v2 prerelease line: `\u003e= 2.0.0-alpha.1 \u003c 2.0.0-beta.3`\n- Fixed in `@prompty/core@2.0.0-beta.3`\n\nThe legacy v1 JavaScript runtime had a historical hardening change for this issue. During the v2 TypeScript runtime rebuild, the loader again called `gray-matter` directly and the vulnerable behavior was present in the v2 prerelease packages until `2.0.0-beta.3`.\n\n## Impact\nApplications that load untrusted `.prompty` files, user-provided prompt paths, or prompt bundles from less-trusted locations could execute arbitrary JavaScript in the host Node.js process during frontmatter parsing.\n\n## Remediation\nUpgrade `@prompty/core` to `2.0.0-beta.3` or later.\n\nThe fix explicitly overrides the `js` and `javascript` gray-matter engines and rejects JavaScript frontmatter in `.prompty` files. Prompty frontmatter is YAML-only; executable frontmatter is unsupported. A regression test now verifies that `---js` frontmatter is rejected and not evaluated.\n\n## Fix details\nFixed by commit `c27402da2487075be577f06aa79df627fb9d6853` and released via `typescript/2.0.0-beta.3`.","aliases":["CVE-2026-53597"],"modified":"2026-07-17T20:00:17.099953006Z","published":"2026-07-17T19:53:34Z","database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-07-17T19:53:34Z","nvd_published_at":"2026-07-16T16:19:12Z","cwe_ids":["CWE-94"]},"references":[{"type":"WEB","url":"https://github.com/microsoft/prompty/security/advisories/GHSA-c4gh-rv8h-q9vw"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53597"},{"type":"WEB","url":"https://github.com/microsoft/prompty/commit/c27402da2487075be577f06aa79df627fb9d6853"},{"type":"PACKAGE","url":"https://github.com/microsoft/prompty"}],"affected":[{"package":{"name":"@prompty/core","ecosystem":"npm","purl":"pkg:npm/%40prompty/core"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.0.0-alpha.1"},{"fixed":"2.0.0-beta.3"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-c4gh-rv8h-q9vw/GHSA-c4gh-rv8h-q9vw.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}