Hardcoded secrets, unverified tokens, and other common JWT mistakes

JWT (JSON Web Token) is an open standard designed to securely transmit information between two parties in a JSON object, although its security relies heavily on proper implementation. A security review of 2,000 npm modules using popular JWT libraries in Node.js revealed several common mistakes such as hardcoded secrets, allowing the 'none' algorithm for signing, improper token validation, and sensitive data exposure. These issues can lead to vulnerabilities, enabling attackers to forge tokens or manipulate data. The review suggests avoiding these pitfalls by separating JWT secrets from code, ensuring proper token validation, and avoiding the inclusion of sensitive information in tokens. Tools like Semgrep can help detect these vulnerabilities, and integrating security scans into CI processes can prevent them from entering the codebase.