MV3 host permission install prompt

[rebloor]

Description

Addresses the documentation needed for Bug 1889402 Grant origin permissions during install for mv3, including:

• a release note
• a note in the description of the host permissions key

Related issues and pull requests

Related update to the Extension Workshop Manifest V3 migration guide mozilla/extension-workshop#1887

[github-actions]

Preview URLs

• /en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/host_permissions
• /en-US/docs/Mozilla/Firefox/Releases/127

External URLs (4)

URL: /en-US/docs/Mozilla/Firefox/Releases/127
Title: Firefox 127 for developers

• https://bugzil.la/1889402 (1 time) (Note! This may be a new URL 👀)
• https://bugzil.la/1893232 (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/host_permissions
Title: host_permissions

• https://bugzil.la/1893232 (1 time) (Note! This may be a new URL 👀)
• https://support.mozilla.org/en-US/kb/extensions-button (1 time) (Note! This may be a new URL 👀)

(comment last updated: 2024-06-27 04:16:46)

[Rob--W]

Suggested change

> **Note:** From Firefox 127. `host_permissions` for Manifest V3 extensions is considered a required permission and displayed to users during installation. However, if an extension update grants new host permissions, these are not shown to the user. See ([Firefox bug 1893232](https://bugzil.la/1893232))

> **Note:** Until Firefox 126, Firefox did not include requested host permissions of Manifest Version 3 extensions in the install prompt. Starting from Firefox 127, host permissions listed in `host_permissions` and `content_scripts` do appear in the install prompt. However, if an extension update requests new host permissions, these are not shown to the user. See ([Firefox bug 1893232](https://bugzil.la/1893232)).

On wording: "required" is not accurate.

The previous paragraph tries to emphasize that host_permissions are optional, and that is still the case: users can revoke them at any time.

The wording as written is technically true but potentially overstating the unreliability of them.

In practice:

• Chrome shows the permissions in the install prompt.
• Firefox 127 shows the permissions in the install prompt. Up until Firefox 126, host permissions were not shown in the install prompt. Starting from 127, they are. However, when a new permission is added in an update, Firefox will not show any prompt for it. Extensions who rely on the new host permissions are encouraged to use the permissions.contains API after install (runtime.onInstalled) to check whether the permission has been granted and show an onboarding page if needed.

[github-actions]

This pull request has merge conflicts that must be resolved before it can be merged.