There's a r+ patch which didn't land and no activity in this bug for 2 weeks.
:zombie, could you have a look please?
For more information, please visit auto_nag documentation.

Backed out for failures on test_ext_webSocket.js

• backout: https://hg.mozilla.org/integration/autoland/rev/ab524816237c246a054ef8cfb65937fe3315efa5

• push: https://treeherder.mozilla.org/jobs?repo=autoland&revision=540fd6bb70bd35f1d7de0b4e0875c894ce47a9c0&group_state=expanded

• failure log: https://treeherder.mozilla.org/logviewer?job_id=346226649&repo=autoland&lineNumber=3431

[task 2021-07-24T20:27:13.981Z] 20:27:13     INFO -  TEST-START | xpcshell-remote.ini:toolkit/components/extensions/test/xpcshell/test_ext_webSocket.js
[task 2021-07-24T20:27:14.785Z] 20:27:14  WARNING -  TEST-UNEXPECTED-FAIL | xpcshell-remote.ini:toolkit/components/extensions/test/xpcshell/test_ext_webSocket.js | xpcshell return code: 0
[task 2021-07-24T20:27:14.785Z] 20:27:14     INFO -  TEST-INFO took 804ms
[task 2021-07-24T20:27:14.785Z] 20:27:14     INFO -  >>>>>>>
[task 2021-07-24T20:27:14.785Z] 20:27:14     INFO -  (xpcshell/head.js) | test MAIN run_test pending (1)
[task 2021-07-24T20:27:14.786Z] 20:27:14     INFO -  (xpcshell/head.js) | test run_next_test 0 pending (2)
[task 2021-07-24T20:27:14.786Z] 20:27:14     INFO -  (xpcshell/head.js) | test MAIN run_test finished (2)
[task 2021-07-24T20:27:14.786Z] 20:27:14     INFO -  running event loop
[task 2021-07-24T20:27:14.787Z] 20:27:14     INFO -  xpcshell-remote.ini:toolkit/components/extensions/test/xpcshell/test_ext_webSocket.js | Starting check_remote
[task 2021-07-24T20:27:14.787Z] 20:27:14     INFO -  (xpcshell/head.js) | test check_remote pending (2)
[task 2021-07-24T20:27:14.787Z] 20:27:14     INFO -  TEST-PASS | xpcshell-remote.ini:toolkit/components/extensions/test/xpcshell/test_ext_webSocket.js | check_remote - [check_remote : 1] useRemoteWebExtensions matches - true == true

Fixed test_ext_webSocket.js which landed in-between.

https://hg.mozilla.org/mozilla-central/rev/3881437c0949

Summary for documentation: for MV3 extensions, the permissions keys is only used for API permissions, while the new host_permissions key is used for OriginPermissions (or MatchPatterns).

https://phabricator.services.mozilla.com/D118305#change-usLdbxehvswa

Does this need to documenting ahead of the overall MV3 changes?

Not really, this is part of the manifest format changes for MV3 and can be done at the same time.