Craft is a content management system (CMS). Craft CMS 5 allows reuse of TOTP tokens multiple times within the validity period. An attacker is able to re-submit a valid TOTP token to establish an authenticated session. This requires that the attacker has knowledge of the victims credentials. This has been patched in Craft 5.2.3.
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.