Server-side template injection in @prompty/core Nunjucks renderer (CVE-2026-73299)

The TypeScript Nunjucks renderer in @prompty/core evaluated untrusted .prompty template bodies with unrestricted JavaScript member access. An attacker-controlled template could traverse constructor and prototype properties to execute arbitrary JavaScript in the host Node.js process. Applications rendering untrusted, community-supplied, cloned, or LLM-generated .prompty files are exposed to attacker-controlled code execution with the privileges of the Node.js host process. Affected versions: - @prompty/core <= 0.1.4 - @prompty/core <= 2.0.0-beta.4 We recommend updating to: @prompty/core >= 0.1.5, @prompty/core >= 2.0.0-beta.5. CVSS 10.0 · our assessment: act_now Reference: https://github.com/microsoft/prompty/security/advisories/GHSA-w28w-gp39-m4p6 Details: https://vuln.today/cve/CVE-2026-73299