EME plugins will use whatever user-hostile platform-specific opaque techniques necessary to communicate with the host OS in their attempt to ensure compliance.

If the browser interferes with them, or the OS can't promise a "secure" chain from plugin-output > display, they can just refuse to stream the content.

You can bet EME plugins will be highly platform specific, and poorly supported, if at all, on platforms that respect their users.

Firefox will heavily sandbox their EME plugins. They get no direct access to the host OS.

Anyone taking bets on how long it will be before CDMs start requiring extensions that allow access to platform Output Protection/HDCP mechanisms?

If nothing else, the standard already allows for the CDM to access the network (albeit managed by the user-agent) which means, for example, it could ping Microsoft to ask about this particular Win10 computer (as identified by user agent, IP address, and/or user account data from the content provider).

Netflix/Microsoft/Hollywood/etc. aren't going to stop until they can close the loop as much as possible, with MS and hardware manufacturers already working to tighten things from the other end (see HDCP and the various frameworks for "protected content" that MS has been working towards).

Either providers will push to integrate those platform-level frameworks, or they'll just stop offering content to web browsers entirely.

> with MS and hardware manufacturers already working to tighten things from the other end (see HDCP and the various frameworks for "protected content" that MS has been working towards).

HN users would do well to keep this in mind the next time they are singing MS's praises about how MS are embracing open source and becoming the savior of all things programming.

Apple and Google also have platform-level frameworks on their OSes.

Probably not while Mozilla Foundation is a US organization.