The FBI spied on a private Signal group chat of immigrants’ rights activists who were organizing “courtwatch” efforts in New York City this spring,
[They] gained access to conversations in a “courtwatch” Signal group that helps coordinate volunteer activists who monitor public proceedings at three New York federal immigration courts.
The FBI’s report […] does not make clear how the bureau accessed the Signal group. […] typically, the only way law enforcement can access messages is if they are directly included in the chat, are sent copies from a participant or have access to a member’s unlocked phone.
IMO, E2EE in group chats is an indispensable feature. That being said, this story is a reminder that the primary threat model on a group chat is always the other people on the chat.