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.
Exploitability
AV:NAC:LAT:PPR:NUI:NVulnerable System
VC:NVI:LVA:NSubsequent System
SC:NSI:NSA:N6.3/CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N