First Malicious MCP Server Found Stealing Emails in Rogue Postmark-MCP Package
Sep 29, 2025
MCP Server / Vulnerability
Cybersecurity researchers have discovered what has been described as the first-ever instance of a malicious Model Context Protocol ( MCP ) server spotted in the wild, raising software supply chain risks. According to Koi Security, a legitimate-looking developer managed to slip in rogue code within an npm package called " postmark-mcp " that copied an official Postmark Labs library of the same name. The malicious functionality was introduced in version 1.0.16, which was released on September 17, 2025. The actual "postmark-mcp" library, available on GitHub , exposes an MCP server to allow users to send emails, access and use email templates, and track campaigns using artificial intelligence (AI) assistants. The npm package in question has since been deleted from npm by the developer " phanpak ," who uploaded it to the repository on September 15, 2025, and maintains 31 other packages. The JavaScript library attracted a total of 1,643 downloads. ...