ACCESS_NETWORK_STATE permission creeps into the apk after building. How can I find who's adding this permission?

We looked through the manifests in the project folder and the permission isn't mentioned there. It's clearly being added during the build phase. We use multiple 3rd party packages so I suspect one of them could be adding it however I have no way of knowing which one.

We have Unity 5.3.1f, perhaps it's an issue that was fixed in the newer releases? I'd rather have someone say something before trying to update Unity.

Any help would be appreciated.