[grosbisou]

Curious about the 2. JWTs are signed via a secret key right? Couldn't the backend verify the signature and reject the token. I am pretty confident most JWT implementation does that automatically.

The dude just didn't think about that or looked into how JWTs work. Which I believe is even worse :<

[peller]

I think you're thinking of a different attack vector, namely, forging a new JWT.

Whereas the parent poster said "what would happen if I stolen his token" (for example, via XSS). So in that case, it's a legit token in the hands of a bad actor, and the signature would be still be valid as far as the backend could tell.