PraisonAI is a multi-agent teams system. Prior to 0.1.6, praisonaiplatform/services/authservice.py falls back to the public dev-secret-change-me HS256 signing key when PLATFORMJWTSECRET is unset, while the startup and token-issuance guards are disabled because PLATFORMENV also defaults to dev. An unauthenticated attacker can sign a JWT containing an attacker-chosen sub value, and AuthService.verifytoken() accepts it as an authenticated identity, enabling user or workspace-owner impersonation when a target identifier is known. This vulnerability is fixed in praisonai-platform 0.1.6.