Hi,
thanks for your interest, sadly we have need to add this, on firefox only, for enable the capacity of take screenshoot automaticaly on user demande in "report a bug" popup section, when we check the corresponding checkbox, actually, in firefox only, we need this sad permission as you can read at: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/tabs/captureVisibleTab
In webkit based browser we currently only use the activeTab permission for this feature.