UTMStack before 11.2.16 contains an account enumeration vulnerability that allows unauthenticated attackers to determine registered email addresses by observing differing HTTP responses from the POST /api/account/reset-password/init endpoint. Attackers can submit arbitrary email addresses and distinguish registered accounts, which return 200 OK, from unregistered accounts, which trigger a 500 Internal Server Error with backend error details, enabling targeted phishing or credential attacks.