According to the [https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_manifests#native_messaging_manifests](Native messaging manifests spec), `path` may be relative to the manifest itself on Windows. So I think this is a bug.
Bug 1837830 Comment 5 Edit History
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According to the [Native messaging manifests spec](https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_manifests#native_messaging_manifests), `path` may be relative to the manifest itself on Windows. So I think this is a bug.