fix(msteams): secure inbound defaults and ref persistence

Default Microsoft Teams inbound auth validation to enabled, update the README to match, and prevent denied senders from persisting conversation refs before allowlist checks pass.

Made-with: Cursor

nanobot/channels/msteams.py

@@ -57,7 +57,7 @@ class MSTeamsConfig(Base):
     allow_from: list[str] = Field(default_factory=list)
     reply_in_thread: bool = True
     mention_only_response: str = "Hi — what can I help with?"
-    validate_inbound_auth: bool = False
+    validate_inbound_auth: bool = True
 
 
 @dataclass
@@ -116,9 +116,9 @@ class MSTeamsChannel(BaseChannel):
 
         if not self.config.validate_inbound_auth:
             logger.warning(
-                "MSTeams inbound auth validation is DISABLED. "
+                "MSTeams inbound auth validation was explicitly DISABLED in config. "
                 "Anyone who knows the webhook URL can send messages as any user. "
-                "Set validateInboundAuth: true in config for production use."
+                "Only disable this for local development or controlled testing."
             )
 
         self._loop = asyncio.get_running_loop()
@@ -274,6 +274,14 @@ class MSTeamsChannel(BaseChannel):
                 logger.debug("MSTeams ignoring empty message after Teams text sanitization")
                 return
 
+        if not self.is_allowed(sender_id):
+            logger.warning(
+                "Access denied for sender {} on channel {}. "
+                "Add them to allowFrom list in config to grant access.",
+                sender_id, self.name,
+            )
+            return
+
         self._conversation_refs[conversation_id] = ConversationRef(
             service_url=service_url,
             conversation_id=conversation_id,