#deltachat is secure against server-side group membership changes but for a very different reason than #signal which keeps encrypted group membership data in a central store.

Delta Chat has _no_ central store but implements a rigidly tested #p2p group membership model where servers play no role github.com/chatmail/models/tre…

Both signal and delta chat are safe against recently published attacks against #whatsapp that can add members to chats, breaking end to end encryption. arstechnica.com/security/2025/…

WhatsApp provides no cryptographic management for group messages

The weakness creates the possibility of an insider or hacker adding rogue members.

^{Dan Goodin (Ars Technica)}