This advisory has been withdrawn due to an incorrect package mapping error. This link is maintained to preserve external references.
Original Description
Summary
Using a recovery flow with an identification stage an attacker is able to determine if a username exists.
Impact
Only setups configured with a recovery flow are impacted by this. Anyone with a user account on a system with the recovery flow described above is susceptible to having their username/email revealed as existing.
Details
An attacker can easily enumerate and check users' existence using the recovery flow, as a clear message is shown when a user doesn't exist. Depending on configuration this can either be done by username, email, or both.