CVE-2026-53597 in prompty
Summary
by MITRE • 07/16/2026
Prompty is a markdown file format (.prompty) for LLM prompts. From 2.0.0-alpha.1 until 2.0.0-beta.3, the @prompty/core TypeScript loader in runtime/typescript/packages/core/src/core/loader.ts used gray-matter without overriding executable js and javascript frontmatter engines, allowing an attacker-controlled .prompty file with ---js frontmatter to execute arbitrary JavaScript during prompt loading. This issue is fixed in version 2.0.0-beta.3.
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Analysis
by VulDB Data Team • 07/16/2026
The prompty markdown file format represents a specialized document structure designed for organizing and managing large language model prompts within development environments. This format leverages yaml frontmatter to define metadata and configuration parameters that guide how prompts are processed and executed. The vulnerability affects the @prompty/core TypeScript loader component which serves as the runtime mechanism for parsing and loading prompty files during application execution.
The technical flaw stems from the loader's implementation in runtime/typescript/packages/core/src/core/loader.ts where gray-matter library is utilized without proper configuration of its frontmatter engines. Specifically, the default executable engines for javascript and js frontmatter types remain enabled, creating a path for arbitrary code execution. When an attacker crafts a malicious .prompty file containing ---js frontmatter section, the loader processes this content through the vulnerable gray-matter parser, executing any JavaScript code embedded within the frontmatter block during normal prompt loading operations.
This vulnerability represents a classic server-side request forgery and code injection issue that falls under CWE-94 - Improper Control of Generation of Code and CWE-74 - Improper Neutralization of Special Elements in Output Used by a Downstream Component. The attack vector operates through the legitimate file parsing functionality, making it particularly dangerous as it can be exploited through normal application workflows without requiring elevated privileges or specialized attack vectors. The vulnerability is classified under ATT&CK technique T1059.007 - Command and Scripting Interpreter: JavaScript which specifically addresses the execution of JavaScript code in various contexts.
The operational impact of this vulnerability extends beyond simple code execution, potentially allowing attackers to access system resources, exfiltrate data, or compromise the entire application environment. Since the loader operates during runtime prompt loading processes, any application utilizing prompty files becomes vulnerable, particularly those that process user-provided content or load configuration from external sources. The vulnerability affects a specific version range indicating that developers who have not upgraded beyond 2.0.0-beta.3 remain at risk.
Mitigation strategies should focus on upgrading to version 2.0.0-beta.3 or later where the issue has been resolved through proper configuration of gray-matter engines. Organizations should also implement strict input validation for any user-provided prompty files and consider implementing sandboxing mechanisms around file parsing operations. Additional defensive measures include restricting file access permissions, monitoring for unusual file processing patterns, and ensuring that applications do not load prompty files from untrusted sources without proper sanitization. The fix demonstrates the importance of properly configuring third-party libraries and understanding their default security configurations to prevent unintended code execution pathways.