An intermediate certificate, which chains up to a root included in Mozillas root store, was loaded into a firewall device that performed SSL man-in-the-middle (MITM) traffic management. It was then used, during the process of inspecting traffic, to generate certificates for domains the device owner does not legitimately own or control. The Certificate Authority (CA) has told us that this action was not permitted by their policies and practices and they have revoked the intermediate certificate. Mozilla is adding the revoked certificate to OneCRL, our mechanism for sending revocation information to Firefox which will be shipping in Firefox 37.”]
Source: https://blog.mozilla.org/security/2015/03/23/revoking-trust-in-one-cnnic-intermediate-certificate/