Snyk has detected a security issue in the provided Node.js code that uses the insecure JSON web token method `jwt.decode()` from the `jsonwebtoken` library, which can lead to broken authentication. The vulnerable code fails to verify the signature of the JWT token, allowing anyone to tamper with it and still have the application accept it as valid. Snyk's detection highlights the importance of using secure methods like `jwt.verify()` to ensure the integrity of JWT tokens. Additionally, the example Node.js code has other security issues, including hardcoded sensitive data, insufficient logging, rate limiting, token expiration, and improper use of refresh tokens. To secure a REST API with JWT, it is essential to implement strong secret keys, HTTPS transmission, proper token expiration and revocation strategies, and managed refresh tokens.