My solution for CSP2 and CSP3 challs in WeCTF 2021. https://github.com/wectf/2021/tree/master/csp3
The python app was hosted on a server we controlled (http://bln.nu:1337), the
payload sent to the "admin" browser was simply that url.
The server would first create a post on the CSP site, the content did not matter, I just needed the hash. The page would open an iframe containing the hash, as well as an injection for the unserialize call being made in the PHP code on the &user GET parameter (see serialize.php). This would tamper with the CSP Header sent back to set