Course

In this course, you will learn how to exploit a weakness in the JSON Web Token (JWT) implementation used for authentication. Upon successful login, users receive a JWT stored in a cookie. The focus is on the `kid` parameter in the JWT header, which stands for "key identifier." This parameter is used without proper escaping, leading to multiple vulnerabilities such as SQL injections and directory traversals. You will automate testing, tamper with the `kid` value, and find a way to use a predictable file to sign a malicious JWT, ultimately gaining administrator access.

The exercise demonstrates that the security of a signed token is only as strong as the handling of the signature. By exploiting a vulnerability in the key retrieval process, you can bypass the signature with a weak key. This course offers a comprehensive guide, from creating a user and inspecting the token to using Python scripts for the exploitation process, ensuring a thorough understanding of JWT vulnerabilities.