What does this PR do?

Resolves #8389

🚨 Security Incident Report

A medium-high severity authorization vulnerability was identified within the WhatsApp Bridge component. Under the default configuration (WHATSAPP_MODE = 'self-chat'), the system was inadvertently processing inbound payloads from unauthorized third-party senders. This occurred because the absence of an explicitly defined WHATSAPP_ALLOWED_USERS list was defaulting to a permissive state (true), effectively bypassing the intended self-isolation constraints and exposing the bridge to public interaction.

🔬 Vulnerability Analysis

The root cause stems from a logical flaw in the boundary validation checks across two modules:

1. In allowlist.js, an empty evaluation set inherently returned a bypass (return true), violating the principle of least privilege by failing open instead of failing closed.
2. In bridge.js, the routing logic did not distinctly enforce the self-chat execution mode boundary when processing non-origin (!msg.key.fromMe) events.

🛡️ Mitigation Strategy

The authorization architecture has been patched to enforce a strict "deny-by-default" policy:

• Fail-Closed Enforcement (allowlist.js): An empty or uninitialized allowlist now correctly resolves to return false, explicitly denying access to unregistered external identifiers.
• Strict Mode Isolation (bridge.js): Injected a pre-computation gateway check that actively inspects WHATSAPP_MODE. If the environment is constrained to self-chat, all non-origin payloads are immediately dropped (continue) prior to any allowlist evaluation.

🔒 Security Impact

• Complete isolation restored for default self-chat deployments.
• Unintended public interaction vectors neutralized.
• Enforced zero-trust validation on empty configuration arrays.

Related Issue

Fixes #

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

How to Test

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform:

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

For New Skills

• This skill is broadly useful to most users (if bundled) — see Contributing Guide
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