In Docker CE and EE before 18.09.8 (as well as Docker EE before 17.06.2-ee-23 and 18.x before 18.03.1-ee-10), Docker Engine in debug mode may sometimes add secrets to the debug log. This applies to a scenario where docker stack deploy is run to redeploy a stack that includes (non external) secrets. It potentially applies to other API users of the stack API if they resend the secret.