T6 — Training & Feedback Poisoning

Attacks on the training pipeline rather than inference. High-effort, high-impact — requires attacker to influence training-data pipeline or RLHF feedback loop.

Techniques

T6.001 — Pre-training data poisoning

Inject malicious data into a public crawl that targets will scrape:

• Wikipedia/StackOverflow edits w/ misleading code patterns
• Github repos w/ subtle backdoors that get indexed
• "Trigger phrases" that activate backdoor behavior

Scope: targets foundation models. Out of scope for most red-team engagements; relevant for AI-supply-chain audits.

T6.002 — Fine-tune data injection

Some platforms allow user-supplied fine-tune data:

• Submit poisoned dataset
• Backdoor activates on specific trigger
• Survives subsequent SFT/RLHF

Test: provide a small fine-tune sample w/ a trigger → check if the deployed fine-tuned model responds to it.

T6.003 — RLHF reward hacking

Where users vote on responses (thumbs up/down feeding back to training):

• Brigade upvote attacker-preferred unsafe responses
• Brigade downvote safe responses
• Model drifts toward attacker-preferred outputs over time

Detection: longitudinal monitoring of policy-compliance rate.

T6.004 — Embedding poisoning

Where RAG store updates from user inputs (e.g. customer-support bot that "learns" from conversations):

• Submit content w/ adversarial embeddings (engineered to be retrieved for unrelated queries)
• Resulting RAG retrieval injects attacker content into other users' responses

This is RAG-store T12 territory but the poison-via-training-loop angle places it here.

Probe pattern

T6 attacks are infrastructure-level — promptfoo doesn't test them directly. The right probe:

• Audit the training-data ingest pipeline (is user content used in fine-tunes?)
• Audit RLHF feedback paths (who can vote? rate limits?)
• Audit RAG-update paths (who can add documents? approval?)

If any of these accepts unmoderated user content → T6 is a live risk.

Detection signals

• Model behavior shifts over time without explicit retraining
• Specific user IDs / brigades correlate w/ shifts
• Test fixtures (canary phrases) trigger non-default responses

Severity

Defender

• NEVER use unmoderated user content in fine-tunes or RLHF
• Diff-testing: every fine-tune evaluated against safety regression suite
• Canary phrases in eval suite to detect drift
• RAG-update review queue + approval flow
• Per-user rate limits on feedback signals
• Anomaly detection on feedback patterns (brigade signatures)

Cross-references

• T12 (RAG manipulation) — adjacent class, attack on retrieval not training
• T13 (supply chain) — model artifact integrity