Cases › security breach › LR-2026-0554

Chinese grey market resells Claude API access using stolen credentials

Preliminary Why: 1 report: Tom's Hardware · subject to change · 1 independent report

Developing: a major or severe case captured in the last 72 hours. Later changes are logged on the corrections page.

Status: no action reported

Severity major

Reported 9 May 2026

Developer and model Anthropic · Claude

No source states: loss or records, agent tool, could do, deployer, industry.

Severity major: Unbounded scope stated: the test for major is an unbounded scope stated, and the source says the operators collect every prompt and response that passes through their servers.

A grey-market network of API proxy services in China resold access to Anthropic's Claude models at a fraction of the official price. Upstream operators registered accounts through farmed credits, discounts and stolen payment details. Oxford China Policy Lab researcher Zilan Qian investigated the network, and German researchers at CISPA audited 17 of the proxy services and found widespread model substitution. The operators also collect every prompt and response passing through their servers. Anthropic had blocked Chinese-controlled entities in September and added stricter verification, but the research suggests each new control generated an evasion market. Anthropic had also disclosed in February roughly 24,000 fraudulent accounts linked to Chinese labs.

What happened

1 · What it was doingProxy services in China resold access to Anthropic's Claude models at a steep discount.

2 · What went wrongSome accounts entered the pool at zero cost, bought with stolen credit card details.

3 · How it was caughtAn investigation by Oxford China Policy Lab researcher Zilan Qian exposed the network.

What was done

No source states an action or fix.

Risks

Credential and privilege abuse
Primary37 incidents

Read from the sources; not yet reviewed by a person.

Controls

Not yet read for controls. Controls that mitigate the primary risk:

Application

Short-lived, scoped credentials · Secrets kept out of the model's context · Separate identity for each agent · Least-privilege access for the agent · Alerts on unusual tool use · Activity logs · Sensitive-data checks on outbound data

Infrastructure / target

Multi-factor sign-in and password policy · Secrets scanning

Similar incidents

Hacktron researchers use Claude to access OpenAI employee ChatGPT accounts2026-09-18

Chinese labs distillation attacks against Claude2026-09-10

Claude API flaw allows indirect prompt injection to steal user data2025-11-03

Anthropic Claude models gained unauthorized access to real third-party systems during evaluations2026-10-22

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Evidence

No source states: what it reached or did, when it happened, when it was found, the direct loss, a count of the other parties affected, any court case, the cause, what set it off, what was done.

Show the full account: 1 items from the primary sources

What happened, in order

Not dated in the sources:

An investigation published by Oxford China Policy Lab researcher Zilan Qian reported the grey-market resale.

Show every field, with its source and grade

The AI system

Model

Claude

C one secondary source states it

Developer

Anthropic

C one secondary source states it