CVE-2026-61428: PraisonAI: AgentMail webhook lacks signature verification, allowing unauthenticated message injection and sender spoofing

PraisonAI’s AgentMail bot, when run in webhook (or hybrid) mode, starts an aiohttp webhook server bound to 0.0.0.0 and processes inbound message.received events without verifying any signature/HMAC and without authentication. The sender address and message body are taken directly from the attacker-controlled request body, so any network peer can inject messages into the agent with a spoofed sender (bypassing sender allow/block lists) and have the agent process the content and reply to an attacker-chosen address. Sibling bots (linear.py, whatsapp.py) fail closed when no secret is configured; AgentMail omits the check entirely. Runtime-confirmed; severity Medium.