{"version":"2.1.265","anchor":"slack-relay-envelopemarker-validation-tightened","canonical_anchor":"slack-relay-envelopemarker-validation-tightened","heading":"Slack relay envelope\/marker validation tightened","tier":"internal","area":"Slack Integration","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.265\/e\/slack-relay-envelopemarker-validation-tightened","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.265","markdown":"### Slack relay envelope\/marker validation tightened\n\nSlack integration tightened its rules for spotting genuine start-of-turn messages vs. injected content\n\n**What**\n\nClaude 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:\n\n- 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.\n\n- 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.\n\n**Why**\n\nThis 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.\n\n- Area: Slack Integration\n- Tier: Under the hood\n- Useful: 1\/5\n- Signal: 1\/5"}