Linux distributions, container images, mobile devices come with about 150 root certificates from OpenSSL and Mozilla. Do we really know who is issuing these certificates? Why do we trust random government bodies from the EU, US and China? Why does some post office have the same trust that some telecom operator has? In practice, any one of them can issue a certificate for any domain on the internet.
This talk argues that the default CA trust model is over-permissive and poorly understood. We need to look at what is actually inside common CA bundles.
Solution: Review your ca-bundles drop anything strange. If you develop an important application that must be 100% trustable, pin the certificate.