Affected: PyPI: praisonai

# PraisonAI LinearBot processes unsigned webhooks when `LINEAR_WEBHOOK_SECRET` is missing

## Summary

PraisonAI's LinearBot starts a public webhook listener on `0.0.0.0` and treats `LINEAR_WEBHOOK_SECRET` as optional. When the secret is absent, startup only logs a warning and `_handle_webhook()` skips `Linear-Signature` verification entirely.

An unauthenticated network caller who can reach the webhook endpoint can submit a forged `Linear-Event: AgentSession` request. The forged request is parsed, scheduled for background processing, dispatched to `_handle_agent_session()`, and passed into `BotSessionManager.chat()`. The bot then attempts to post the agent response back to Linear under the configured bot token.

The local PoV is offline and deterministic. It does not contact Linear. It calls the webhook handler directly, monkey-patches the outbound Linear comment path, and proves both sides of the boundary:

- no secret configured: unsigned forged webhook returns `200`, invokes the agent session path once, and attempts one Linear comment; - secret configured: missing and bad signatures both return `401` and do not invoke the agent; - secret configured with valid HMAC: request returns `200` and invokes the agent, proving the control path still works.

## Affected Product

- Repository: `MervinPraison/PraisonAI` - Package: `praisonai` - Components: - `src/praisonai/praisonai/bots/linear.py` - `src/praisonai/praisonai/cli/features/bots_cli.py`

Validated affected:

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