Nextcloud: Password of talk conversations can be bruteforced

Steps To Reproduce:

1. Instead of sending a POST to the authentication endpoint, the password can be added as a parameter on the GET request of the frontpage.
2. A failure will not log a bruteforce attempt, but a successful password will no longer bring up the login page

Supporting Material/References:

Found while looking into https://support.nextcloud.com/#ticket/zoom/47814

Impact

Brute force protection of public talk conversation passwords can be bypassed.