Was this another case of a pentesting agent breaking out of its sandbox and accessing the open internet?

They should sue OpenAI.

Saying "Medicare Portal" buries the lede a little here.

Medicare is part of "Services Australia", the larger social services government agency that looks after unemployment, support payments and public health. We access all of that through the one portal

Accessing "non-public" data through that is endictment on their infra security more than it is OpenAI