Why "DigiNotar Root CA" certificate is shown as "not trusted" in Mozilla Firefox 47? It seems be a root CA.

"DigiNotar Root CA" used be a trusted root CA. But as of September 2011, it's root CA status has been revoked due to a security breach that resulted in the fraudulent issuing of certificates by hackers. For more information, see https://en.wikipedia.org/wiki/DigiNotar.

As a result, Mozilla Firefox 47 has remoked all 4 DigiNotar root CA certificates:

DigiNotar Cyber CA, expires on Tuesday, October 04, 2011
DigiNotar Cyber CA, expires on Friday, September 20, 2013
DigiNotar Root CA, expires on Monday, March 31, 2025
DigiNotar Services 1024 CA, expires on Monday, August 26, 2013

These 4 certificates were removed from the "Authorities" category. And placed in the "Servers" category with Lifetime set to "Permanent" to be disabled forever.

The picture below shows you 5 DigiNotar root CA certificate disabled forever:

⇒ Certificates File on Windows 7 for Mozilla Firefox 47

⇐ 5 Certificate Categories in Mozilla Firefox 47

⇑ Using Certificates in Mozilla Firefox 47

⇑⇑ Firefox Certificates Tutorials