Hackers last year conducted a 'dry run' of SolarWinds breach (news.yahoo.com)

SolarWinds earlier said the backdoored binaries were put into their servers in March 2020, and hinted that the breach happened in 2020 but seems like the breach happened way before.

See related thread regarding the 2018 credentials leak - https://news.ycombinator.com/item?id=25442734