Blake Buchert
Selected work — 2024 to 2026

Five engagements,
written up plainly.

Client names appear where the team agreed to be named. Findings are summarized at the level the write-up was cleared for.

11Engagements delivered
140+Findings filed
6Regression suites shipped
0Findings reopened
Red team2026

Prompt injection at the tool boundary

Northgate Labs — customer support agent
Scope
5 weeks, live staging
Stack
Python harness, OpenTelemetry, GitHub Actions
The problem

A support agent with write access to the billing API was treating retrieved help-center articles as trusted context. Content in those articles could be edited by any partner with a docs seat.

What I did

Built a harness that treats every tool result as attacker-controlled and replays a corpus of injection payloads through the retrieval path. Each case is a test file, so a payload that works once becomes a permanent assertion.

Outcome

Forty-three reproducible cases, four of them able to trigger a refund without user intent. The team moved billing calls behind a confirmation step and adopted the harness as a CI gate — it has blocked two regressions since.

We brought Blake in for a two-week review and kept him for the quarter. The harness he built is now the thing that tells us whether an agent change is safe to ship.
Jackson Leonard — VP Engineering, Northgate Labs
Detection2025

Model exfiltration telemetry

Corvid AI — inference platform
Scope
Full quarter, platform team
Stack
Go, eBPF, Sigma, ClickHouse
The problem

Competitors were suspected of distilling a production model through the public API, but nothing in the logs distinguished bulk distillation from a heavy legitimate customer.

What I did

Instrumented the inference gateway to record query-shape features — diversity, coverage of the output space, pacing across keys — and wrote detections on the patterns distillation produces rather than on raw volume.

Outcome

Time-to-detection on scraping campaigns fell from weeks to under four hours, with a false-positive rate the on-call team accepted without tuning. The rules shipped as Sigma so they live in the existing SIEM.

Rare combination: reads the papers closely, and still ships tooling the on-call team is happy to own. Our detections outlived his engagement, which is the only real test.
Theo Wallace — Director of ML Infrastructure, Corvid AI
Supply chain2025

Signed weights, verified pipelines

Halden Systems — ML platform
Scope
8 weeks
Stack
Sigstore, SLSA, Kubernetes admission control
The problem

Checkpoints moved between research and production by object-storage path. Nothing proved which code and data produced a given file, and nothing stopped an unreviewed checkpoint from being served.

What I did

Added provenance at every step: signed checkpoints, attested build steps for training jobs, and an admission policy that refuses to serve weights without a verifiable chain back to a reviewed commit.

Outcome

Reached SLSA level 3 for the training pipeline. The policy gate caught an unsigned experimental checkpoint on its second day in production — a real incident that never became one.

Blake found the failure we had already convinced ourselves was theoretical, then wrote the test that keeps it from coming back. He left us with a process, not a report.
Ian Haddad — Security Lead, Halden Systems
Threat model2024

Threat review for an agentic payments assistant

Meridian Pay
Scope
3 weeks, design stage
Stack
Architecture review, workshops
The problem

A payments assistant was heading to design review with a plan to let a model read support tickets and initiate transfers in the same session. Nobody could say which boundary was supposed to stop a bad instruction.

What I did

Mapped every place untrusted text reached a privileged action, then ran two workshops where product and platform engineers argued through the abuse cases against their own diagram.

Outcome

The design shipped with a hard separation between reading and acting, per-session spend limits, and a logging schema written before launch instead of after the first incident.

The clearest threat model review our AI team has had. Every finding came with a fix we could actually schedule, and the diagram is still on the wall.
Rafe Bradshaw — CISO, Meridian Pay
Research2024

Poisoning small fine-tune sets

Independent research — published
Scope
Ongoing
Stack
PyTorch, open dataset, write-up
The problem

Teams fine-tune on a few thousand internal examples and assume the set is too small and too private to be worth attacking. The literature mostly studied poisoning at pretraining scale.

What I did

Measured how few corrupted examples are needed to install a durable trigger in a domain-tuned model, then tested which practical data audits — dedup, near-duplicate clustering, label review — actually catch them.

Outcome

Published with a reproducible dataset and an audit checklist. Two of the four audits catch the attack reliably; the write-up is the reference I hand teams before a fine-tuning project starts.

I cite Blake's fine-tune poisoning numbers in nearly every design review I run. It reframed a risk my team was writing off as academic.
Dr. Priya Raghunathan — Research Lead, Vector Institute for Applied Security

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