In affected versions of Octopus Server, OIDC token issuer validation was performed inconsistently. This could result in a token issued from a suitably configured non legitimate issuer being accepted as a token belonging to a service account from a legitimate trusted issuer. Exploitation requires a service account with at least one OIDC identity configured. An attacker would also need to know or guess some details of that identity in order to be in a position to attempt exploitation.