Link Previews: How a Simple Feature Can Have Privacy and Security Risks

Link previews in chat apps can cause serious privacy problems if not done properly. We found several cases of apps with vulnerabilities such as: leaking IP addresses, exposing links sent in end-to-end encrypted chats, and unnecessarily downloading gigabytes of data quietly in the background.

We think link previews are a good case study of how a simple feature can have privacy and security risks. We’ll go over some of the bugs we found while investigating how this feature is implemented in the most popular chat apps on iOS and Android.