Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
Slack IntegrationArea: what it touches
Internal ChangesKind: in v2.1.265,
Internal ChangesSection of the release
What
Claude Code's Slack integration includes text meant to stop malicious prompt injection, where someone tries to sneak fake instructions into a conversation so Claude treats them as legitimate. This defense text has been tightened in two ways:
File-attachment references must now come immediately before the special marker that opens a genuine user turn; previously, other unrelated '[SendFile: ...]' notes were allowed to sit in between.
A new rule states that only the harness (Claude Code's own controlling system) can place this opening marker or lead-in at the very first characters of a turn; if it appears after any other text, it is just ordinary content and not to be treated as authoritative.
Why
This closes a gap that could let someone disguise injected text as a legitimate system-issued marker by inserting distracting content before it, making the Slack integration harder to trick.
