CVE-2026-48063: Baileys has message upsert / hist sync spoofing and app state corruption when using maliciously crafted protocolMessage payload

Any baileys session under the latest version (< 7.0.0-rc12, and < 6.7.22) can be sent a malicious payload via the placeholderResendMessage and trigger a fake messages.upsert event with a fake message key and payload. This allows anyone to spoof messages. The same exploit also allows an attacker to corrupt the app state sync system by sending fake key shares, and also allows for history sync spoofing which also serves the same problem, injecting fake previous context or “on-demand” sync.