In Bug 1729640, we introduced fission.highValue.login.monitor pref to add high-value permission when a login attempt is detected. Note that turning on the pref doesn't necessarily mean we start to isolate high-value sites. Instead, the pref should be turned on prior to enabling isolating high-value sites feature so when the feature is on, we will have the permission stored in the permission manager.

Hi Chris, I guess this is something you should be aware of and decide the timeline to enable it.

the pref should be turned on prior to enabling isolating high-value sites feature so when the feature is on, we will have the permission stored in the permission manager.

Is this a new Android app permission (that will cause the Android app updater to ask the user to accept this permission) or just new metadata in Firefox's own site permissions manager?

farre told me this feature is doesn't require a new Android app permission. It adds a new permission to identify high-value sites in the Firefox permission manager. Since the new permission is set by a callback at site login time, the sooner we enable this login monitoring, the more high-value sites will be flagged in the permission manager. So we should enable this for Android (only) soon.