Rating:

tl;dr

* Leak csrf token bypassing document.domain
* visiting ` /profile/` will not change the nonce
* Leak nonce using dangling markup in firefox
* add xxs payload using the csrf to get the flag

Original writeup (http://blog.bi0s.in/2023/03/28/Web/AnotherSecureStoreNote-LINECTF20232023/).