XF 1.5 Move all external images internally?

So I am having a website where users mostly use external image hosting services such as imgur, minus etc to embed their media into their post. However some of these images are really important as they are used in various guides on our website. I fear that in the future, when the service decides to delete these images (whatever argument or condition they might impose) I would be left with guides and manuals without the images and/or ugly 'could not find media' embeds.

Is there a way to quickly move all externally embedded media to the internal format used by Xenforo?