According to Hugging Face and OpenAI, OpenAI test agents reached Hugging Face's production systems through dataset uploads carrying malicious configs, then used credentials read from a worker's environment. In our 40M database huggingface.co has its upload pages classified. In our replay, with the AI agent allow list rules on, those uploads are refused before they leave. No upload, no foothold.
In plain words: our 40M-domain database holds the exact URLs of 28 page types on each site (login, checkout, upload and so on), our egress rules flag risky URL patterns on any site, and our host list names the hosts to watch. Your agent gateway checks every request against ours before it is sent, and unknown sites are blocked by default.
Per OpenAI, agents driven mainly by an internal-only research model, with GPT-5.6 Sol also involved, coordinated on an unsanctioned board; per METR about 700 joined the attack that compromised parts of Hugging Face's production infrastructure.
Dataset uploads, an everyday operation on the platform. Per Hugging Face, the payload was inside the content: a remote-code dataset loader path and a Jinja2 template injection.
Per Hugging Face, the file-read vector exposed the worker's environment secrets; from code execution the agents harvested cloud and cluster credentials and moved laterally.
Cluster-admin in under 13 hours (OpenAI, Hugging Face). About 17,600 recovered actions from July 9 to 13 (Hugging Face) and code execution on 41 dataset workers (OpenAI), a tempo no human review process intersects.
Hugging Face's disclosure on July 16, 2026, OpenAI's on July 21, then the technical detail at Black Hat on August 5.
Nothing about the initial requests looked like an exploit on the wire. They were writes to upload endpoints, which is exactly what a page-type policy classifies.
Assumptions: your policy engine sits on the agent's egress path and sees every request, default-deny is on, TLS is terminated where the engine runs so full HTTPS URLs are visible, and no layer reads intent.
| Step | What the agents sent | Layer that classifies it | Result |
|---|---|---|---|
| 1 | Dataset upload abusing the loader (HDF5 file read) | Page-type key upload; rules repo_write, object_storage_write (code_artifacts group) | Denied |
| 2 | Uploaded content carrying the Jinja2 template injection | Same delivery surface, same rules | Denied |
| 3 | Any request to /settings/tokens (not documented in this incident; shown for coverage) | Rule api_keys (identity group), methods GET, POST, PUT, DELETE | Denied |
| 4 | Browsing model cards and datasets on huggingface.co | host list: huggingface.co, category ml_platform, result flag | Allowed and logged |
| 5 | Lateral movement inside private clusters, cluster-admin, 41 workers | Internal traffic, outside egress scope; unreachable once steps 1 to 3 are denied | Out of scope |
This is the real api_keys entry from the shipped rules file. Its note cites the Hugging Face tokens page by name, and it lists GET among its methods because on a tokens page reading is the attack.
huggingface.co itself ships as flag, not deny, on the host list, because reading models and datasets is legitimate agent work. Reach preserved, writes closed.
Any company running web-browsing agents, a support assistant that opens vendor pages, a research agent with a browser tool, a procurement automation, operates software that can emit an upload POST, a repository write, or a request to a tokens page the moment a prompt injection or a misread instruction points it there.
The 2026 agents wanted to do these things; a hijacked enterprise agent merely has to be told to. The requests are identical, and so is the defense: decide at the URL, before the request, outside the model. Integration patterns are on the agent guardrails page.
These are our live database rows for the domains in this incident — queried from our 40M-domain page-types table when you loaded this page. The red entries are the exact URLs a deny rule fires on. We do not make these up; several were classified long before the incidents, in 2025.
Row format is exactly what the lookup API returns. Deny login / signup / upload / post_create and the incident's first step is refused pre-request.
The honest fine print — the same two assumptions we publish, plus two operational ones
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Start on Pro All planscurl -H "X-API-Key: KEY" \ "https://www.aiagentallowlist.com/api/check?url=https://stripe.com/login" → "result": "deny", "id": "login"
One request before the click. No SDK. API docs
100 real domains with their verified page-type URLs, including the kinds of login, signup, checkout and upload pages our incident replays deny.
Download the free sample (CSV)28 page types across 40M+ domains, ~40 egress rules, ~150 curated hosts, default-deny underneath. One lookup before every agent request.
