README.md

Granny's Cookie Factory

Here at Granny's Old-Fashioned Home-Baked Cookie Factory, we pride ourselves on our cookies AND security being the best in the business. Start here: https://jerseyctf-cookie-factory.chals.io/

Recognize that the user cookie is a JWT
Decode it to see that the data has the structure {"username": ...}
On the dashboard page, read the attached CVE to learn the the vulnerability is a user-controlled alg parameter
Realize that the header and data are Base64 encoded
Set the algorithm to "none" and Base64-encode the header section
Set the username to "admin" and Base64-encode the data section
Leave the signature section blank
Flag: jctf{GEEZ_WHAT_A_TOUGH_COOKIE}