I got the CERT_UNTRUSTED when I tried to run bower install command to install components.
For example, I got this error when I ran the following:
bower install bootstrap-sass-official --save
The output was:
bower error Request to https://bower.herokuapp.com/packages/bootstrap-sass-official failed: CERT_UNTRUSTED
Note: This is not a package specific error. This happens when you try to install any package, not just with bootstrap-sass-official.