Comment by GOATS-

There are devices out there with vulnerable TEEs (trusted execution environments), where DRM operations commonly happen. You can then extract L1 keys from those environments - for example with the Nexus 6[0] NVIDIA Shield[1].

[0] https://googleprojectzero.blogspot.com/2017/07/trust-issues-...

[1] https://nvidia.custhelp.com/app/answers/detail/a_id/4682/~/s...