Most installation scripts these days have this particular pattern:
curl -fsSL <url> | sh --- and usually run as root
Some sites might even have a disclaimer about running this as root and to check for errors. However, this isn't very secure, you're depending on the CA infrastructure and https to provide security. Why are sites doing it this way when you could, in addition to having transport over https, have them as signed releases as well - wouldn't non-repudiation as well as file integrity be better? What do most administrators do after downloading this.