A prototype pollution vulnerability exists in the forge.http client of node-forge before version 1.4.1. The client improperly stores cookies from Set-Cookie headers in a plain object keyed by cookie name and path, allowing a malicious server to use cookie names like '__proto__' or 'constructor' to modify Object.prototype or Object. This can lead to adding or deleting properties on Object.prototype, potentially altering application logic or breaking functionality. The issue is fixed in node-forge 1.4.1 by ignoring such dangerous cookie names and paths.