Trying to understand exploit

[cat-pa]

Hi,

I just happen to found out the poc. Would you be willing to share a bit more detail into what CTF this is and any potential way I can learn how to exploit this?

so far I understood that it gives you the HMAC key that lets you decode class files. But I am still not sure given a target I know is vulnerable how to go about it.

If this is not the right place to engage please let me know