Thanks for the reply! That makes sense and it's interesting to see the limitations of the "web extension" framework. The following isn't meant to try to convi

Thanks for the reply! That makes sense and it's interesting to see the limitations of the "web extension" framework. The following isn't meant to try to convince you to use any particular solution (I don't have any skin in the game), just some ideas in case you get fed up even more by the problems with implementing DRM in your own browser. Listening to a socket and reading local files is possible with "Native messaging"[1]. In brief you have a small application running in the background, outside the browser, which can listen to sockets or read local files, and your browser extension communicates with it. This does bring added complexity and might (haven't tested) bring additional latency, possibly making it unacceptable. [1] https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_messaging https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web...