Obviously there is massive information about the SolarWinds Orion hack itself of the malicious DLL injected into the update: https://www.fireeye.com/blog/threat-research/2020/12/evasive-attacker-leverages-solarwinds-supply-chain-compromises-with-sunburst-backdoor.html
But how did the SolarWinds company themselves get infiltrated? Are details of that available?
Also, was the update to the Orion software put live on their HTTP source by the hackers, or approved and put live by someone within the company?
How was the code injected into the DLL? In the source code or post-build?
I’m looking for technical details about the source of the compromise, not the chain reaction from it.