Our dev team is debating authentication mechanisms. How do hackers exploit APIs through token theft and improper JWT validation? If an application leaks a bearer token, how do bad actors replay that token against secure endpoints without triggering rate limits?
3 answers
Hackers compromise APIs through token theft by harvesting JSON Web Tokens (JWTs) from insecure client-side storage like local storage or browser cookies via Cross-Site Scripting (XSS). Once an attacker obtains a valid bearer token, they pass it in the Authorization header of their own automated scripts. Furthermore, if the API backend fails to validate the cryptographic signature of the JWT, handles expiration claims poorly, or accepts the none algorithm in the header, the hacker can forge tokens to assume any identity they choose.
If the token signature is actually verified properly on every request, can a hacker still exploit the API simply by using an intercepted token before it expires?
Attackers capture insecurely stored tokens and replay them against public API paths to systematically drain databases before the tokens can expire.
Very true, Diana. That is why short token lifespans and robust revocation lists are absolutely vital to mitigate the damage of an intercepted token.
Yes, absolutely. If the token is valid and unexpired, the API will treat the hacker as the legitimate user. Without behavior analytics or IP binding, the system cannot distinguish the attacker's requests from normal user activity.