A new analysis of TM Signal’s source code appears to show that the app sends users’ message logs in plaintext. At least one top Trump administration official used the app.

TeleMessage, the app that President Donald Trump’s former national security adviser, Mike Waltz, appeared to use to archive his group chats, has suspended all services after hackers claimed to have stolen files from it.

TeleMessage lets users archive their chats in secure messaging apps. However, the hacker reportedly found that TeleMessage’s archived chat logs aren’t end-to-end encrypted, allowing them to access the contents of certain messages, government official contact information, and login credentials for the service’s backend.