WhatsApp isn’t the only messenger lacking cryptographic assurances for new group members. In 2022, a team that included some of the same researchers that analyzed WhatsApp found that Matrix—an open source and proprietary platform for chat and collaboration clients and servers—also provided no cryptographic means for ensuring only authorized members join a group. The Telegram messenger, meanwhile, offers no end-to-end encryption for group messages, making the app among the weakest for ensuring the confidentiality of group messages.
Just use signal is not a valid statement in a world where vast majority of people aren’t using (and won’t use) it. I have been trying to get people to install it and have a total of 6 over several years. They only use it to communicate with me.
If you want your group memberships to be known only by the group members, use Signal.
Or P2P stuff like Briar :)
Or Matrix (warning some assembly required)
That study was 3 years ago, features to create private (invite only) group chats are supported now.
Are parts of matrix closed source?
Just use signal is not a valid statement in a world where vast majority of people aren’t using (and won’t use) it. I have been trying to get people to install it and have a total of 6 over several years. They only use it to communicate with me.