Paperless-ngx: Mail Account Test Connection Leaks Stored IMAP/OAuth Credentials to Attacker-Controlled Host

Paperless-ngx's MailAccountViewSet.test() action, when called with an existing account's ID and a masked password field, reuses the stored password, account_type, refresh_token, and expiration from that existing account while allowing the caller to supply a different imap_server, imap_port, and imap_security in the same request. The test connection then authenticates to the caller-specified server using the real stored credentials. A user holding only object-level change_mailaccount permission on the target account (not full admin) can redirect the test connection to an attacker-controlled IMAP host, causing the real stored IMAP password or OAuth token to be sent to that host.