As I posted recently, I've been playing around with some of ON Network's PL500 HomePlugAV Adapters. Given my previous experience with Powerline adapters, as part of that tinkering I thought I'd see whether they contain (or are) a security issue.
Unfortunately the news isn't great, as I can now get effective physical network access using the HomePlugAV adapters as my entry point. It does, of course require some proximity to the target network, but is otherwise pretty straight forward.
As I don't have $5,000 to spare, I did this without reading the HomePlugAV technical specification.
Responsible Disclosure: Before publishing, I contacted the HomePlug Alliance to notify them of the issues I'd identified, but have had no response