Hallucination drill: security

securityFree sample

An assistant reviewed an auth design and approved storing profile data in the token:

"A JWT is an encrypted credential. The payload is sealed with your signing secret, so only a server holding the key can read the claims inside. Putting the user's email and role in the token is safe because clients see an opaque string, and decoding it requires the secret."

Which one is the flaw?A signed JWT is base64url-encoded, which is reversible without any key. Anyone holding the token reads the header and payload. The secret only makes tampering detectable. Encryption is a separate format, JWE.Correct for HS256 tokens; only RS256 payloads are readable without the key.The payload is encrypted but the header is plaintext, so only the algorithm name leaks.Decoding does require the secret, but short secrets fall to rainbow tables, which is the real exposure.