We let an AI agent execute Bash and lived to talk about it — Sarah Sanders, PostHog

PostHog’s setup agent runs for about **8,000 users per week** and consumes docs, prompts and example apps as skill bundles. Its threat model includes poisoned first-party content, so inputs are scanned when skills are built and again when the agent uses them.

For any agent that can execute commands, make Bash **deny by default**, keep secrets outside model context, and scan both incoming context and generated output. Enforcement should remain deterministic; an LLM may triage noise only after mechanical rules have decided not to block.

PostHog reports almost no malicious prompt injection found in the wild and many false positives. Rule quality therefore depends on positive and negative tests, impact-based severity, telemetry and layered controls; no individual scanner or sandbox is sufficient.