After installation as per http://documentation.magnolia-cms.com/modules/groovy.html#RegistertheGroovyRescueServlet, no matter what command is typed, one gets the response html printed in the console. (see screenshot)
To reproduce this, delete or rename config:/server, configure the rescue servlet, and restart.
Using RescueSecuritySupport (for instance by setting the info.magnolia.cms.security.SecuritySupport=info.magnolia.cms.security.RescueSecuritySupport property) could help, if it wasn't for
To fix this issue, the rescue servlet could set this property or component itself, so users don't have to modify their properties.