→November 2018 CA Communication (Underscores in dNSNames): 2019 --> 2018
After April 30, 2019, underscore characters (“_”) MUST NOT be present in dNSName entries.
This new language will go into effect on December 10,
2019 when the IPR review period for ballot SC12  is completed. At that time, CAs must be prepared to stop issuing publicly-trusted TLS certificates containing the underscore character in any dNSName with validity periods of more than 30 days.
As a participant in Mozilla's CA Certificate Program, we want you to be aware of this important change, and ask that you take any necessary steps to comply. No further action related to this change is requested at this time.