function attach(modification, target) { if (!modification) return; let window = getTargetWindow(target); attachTo(modification, window); // modification are stored per content; `window` reference can still be the // same even if the content is changed, therefore `document` is used instead. add(modification, window.document); <-- window.document causes unsafe CPOW usage when window is a CPOW } function detach(modification, target) { if (!modification) return; if (target) { let window = getTargetWindow(target); detachFrom(modification, window); remove(modification, window.document); <-- window.document causes unsafe CPOW usage when window is a CPOW } else { let documents = iterator(modification); for (let document of documents) { let window = document.defaultView; // The window might have already gone away if (!window) continue; detachFrom(modification, document.defaultView); remove(modification, document); } } }

content/mod is a module that can be used by both the SDK and by add-ons code, and is not cpow-safe.

Our current promise is that high level APIs are e10s ready, but this one is relying on shims and can cause unsafe CPOW usage. Should we block on this?