Seven Common JWT Authentication Mistakes That Expose Production Apps

JSON Web Tokens are widely used for authentication in web and mobile applications, but security flaws in their implementation can lead to token theft, account takeovers, and unauthorized access. A review of production applications highlights seven recurring mistakes, including storing tokens in insecure locations, omitting expiration claims, and trusting unverified token data. Developers are also warned against embedding sensitive information in JWT payloads, since the data is encoded but not encrypted and can be decoded by anyone. Additional risks arise from neglecting token revocation strategies, reusing signing keys across environments, and failing to enforce server-side authorization checks. Addressing these issues requires combining secure token storage, short-lived access tokens, proper validation, and role-based authorization on every protected endpoint.