Tokens in CTFd used for account activation and password resetting can be used interchangeably for these operations. When used, they are sent to the server as a GET parameter and they are not single use, which means, that during token expiration time an on-path attacker might reuse such a token to change user's password and take over the account. Moreover, the tokens also include base64 encoded user email. This issue impacts releases up to 3.7.4 and was addressed by pull request 2679 https://github.com/CTFd/CTFd/pull/2679  included in 3.7.5 release.

While assignment of a user to a team (bracket) in CTFd should be possible only once, at the registration, a flaw in logic implementation allows an authenticated user to reset it's bracket and then pick a new one, joining another team while a competition is already ongoing. This issue impacts releases from 3.7.0 up to 3.7.4 and was addressed by pull request 2636 https://github.com/CTFd/CTFd/pull/2636  included in 3.7.5 release.

In RedpwnCTF before version 2.3, there is a session fixation vulnerability in exploitable through the `#token=$ssid` hash when making a request to the `/verify` endpoint. An attacker team could potentially steal flags by, for example, exploiting a stored XSS payload in a CTF challenge so that victim teams who solve the challenge are unknowingly (and against their will) signed into the attacker team's account. Then, the attacker can gain points / value off the backs of the victims. This is patched in version 2.3.

Incorrect username validation in the registration process of CTFd v2.0.0 - v2.2.2 allows an attacker to take over an arbitrary account if the username is known and emails are enabled on the CTFd instance. To exploit the vulnerability, one must register with a username identical to the victim's username, but with white space inserted before and/or after the username. This will register the account with the same username as the victim. After initiating a password reset for the new account, CTFd will reset the victim's account password due to the username collision.