Is there a way to disable the same origin policy on the Mozilla Firefox browser by toggling a flag in the browser?
This is strictly for development, for not production use.
Please note:
A similar question asked 3+ years ago yielded an accepted answer that recommends users to install a plugin. I consider this less secure and more cumbersome than toggling a flag (e.g. in the about:config, or passing a parameter when starting the browser like in Chrome).
After having tried to find a Firefox setting for various hours, and after having opened a bounty, I think the right answer to this question is:
At the moment of writing (March 2018), it is not possible to disable the same policy origin in Firefox by simply setting a flag.
I would personally recommend people to use Chrome instead for this kind of work, because disabling this setting is very easy, quick and doesn't involve installing third-party software.