Dault dating sites
In short, photos are hosted on an outside company’s servers.
As Joseph Bonneau explained, the main website provides an obfuscated URL for the photo to anyone it deems has permission to view it.
But in Bonneau’s experiment with 16 popular websites, removing the photo from the main website didn't always remove it from the Content Delivery Network; in those cases, anyone who still had the destination URL would be able to view the photo.
This means that Content Delivery Networks can maintain caches of sensitive photos even after users “delete” them, leaving photos vulnerable to being rediscovered or even hacked in the future.