@DTS Engineer
I think your explanation is not entirely accurate. Actually the sandbox is already treating different system components differently. Therefore it seems very unlikely that the sandbox can not distinguish between "allowed" and "forbidden" network traffic.
MapKit is an encapsulated system component, so it is more or less impossible for a Quicklook extension to send random and uncontrolled network requests. All the network access is completely controlled by the system. So it seems extremely unlikely that there are serious security issues here. BTW: in the past, MapKit did work in Quicklook extensions.
On the other hand, WebKit (WKWebView) is(!) working in Quicklook extensions just fine. But unlike MapKit, WebKit is able to do random and uncontrolled network requests, therefore could be a security issue.
Which means the sandbox is actually distinguishing between different system components. The harmless one it does block, the "dangerous" one it let pass.
I do understand that WebKit is "allowed". There are many extensions which need network access (including many of Apple's own), for example to display web link previews, video/audio streams. So it makes much sense that this is possible.
My thoughts:
Instead of making the macOS less useful by blocking all kinds of useful Quicklook extensions, maybe it would be better to simply ask the user for permission, like this is done for other security or privacy related things (like accessing photos, calendar, location services etc). So the user can decide.
And in practice, the user is already forced to enable each Quicklook extension manually in the settings. So it is already impossible that an extension can be used without the knowledge of the user.
Honestly, what is the point in blocking network access of a Quicklook extension, if the Host-App of this extension still has full network access. If an App would do something bad, it does not need its Quicklook extension, it can do this itself and much more.
Also because Quicklook extensions are now always part of their "Host" App, it is impossible to have any invisible hidden extensions lying around, which the suer can forget about. If the App is deleted, the extension is gone automatically as well. So if the macOS tries the Quicklook extension as "dangerous" it would also have to treat the host App as dangerous and would have to apply all restrictions to both. But of course, this would make the whole system completely unusable. In the end we must give the user the opportunity to decide. Does the user trust an App to use it, then this should apply to the Apps extensions as well. For and possible danger it is fine to ask the user for permission, but if the user allows anything, the system doesn't need to block this anyways.
And at the end Apple can still reject a developer certificate to "kill" the App in case it turns out that the App or developer is doing something bad.
