Netflix: "Our team is aggressively taking action to have it taken down."
If you have never heard of Iyuno before (I hadn't), they are responsible for many aspects of localization and accessibility. They sometimes create dubs, add subs, create closed captioning, etc. They also do this for many languages, not just English. In addition, they work on many Netflix projects that are not just anime, adding captioning or descriptive audio for accessibility.
Statement from Iyuno:
Iyuno is aware of a recent security issue, involving unauthorized access to confidential content. Protecting our clients’ confidentiality and ensuring the security of their content is our highest priority. We are actively investigating this security breach to mitigate any potential risks and identify the responsible parties. When there are material changes or information we will make further statements.
I am sure that the Japanese production committees are paying attention to this. Leaks within the industry happen, but the scale of this one is pretty big with entire seasons worth of episodes leaking ahead of time. This situation reminds me of the Zelda series that was in development at Netflix until Nintendo cancelled it due to news leaking out of Netflix.