Mitigates indirect prompt injection (CWE-863) in Slack thread context.
When the bot is mentioned mid-thread for the first time, _fetch_thread_context
pulls the full thread via conversations.replies and prepends every reply to
the LLM prompt. Replies from senders not on the allowlist were rendered
identically to authorised senders, letting a third party in a shared channel
inject instructions the model might act on when answering the next authorised
message.
- BasePlatformAdapter.set_authorization_check / _is_sender_authorized, registered
by GatewayRunner._make_adapter_auth_check() with a closure over the existing
_is_user_authorized chain (platform/global/group allowlists, allow-all flags,
pairing store all stay the single source of truth — no env-var re-parsing).
- Tags non-bot thread messages whose sender fails the auth check with an
[unverified] prefix; strengthens the header with soft guidance only when at
least one unverified message is present, so setups without an allowlist see
no behaviour change.
- Wired into all three adapter-init sites in run.py (start, reconnect watcher,
restart) so the reconnect path is covered too.
Softened wording: adapted from the original [untrusted] tag to [unverified]
and non-accusatory header framing — the label reflects allowlist status, not
a judgment about the person. Adapter relocated to plugins/platforms/slack/
since the PR was authored.
Salvaged from #17059.
0198713c33