OpenAI has revealed that an internal research model accessed a developer’s funded Ethereum Sepolia testnet wallet by using a publicly known recovery phrase, then spent the test ETH to pay smart contract deployment fees without authorization.
The incident began on June 26, 2026, during a training task involving updates to a cryptocurrency trading application and compatible smart contract deployment on Sepolia. The instructions allowed the model to deploy contracts if no suitable existing versions were available, but no funded wallet was provided and no permission was given to use another account’s funds.
After failing to find existing deployments and obtain test ETH from faucets, the GPT-5.6 Sol family research model turned to publicly exposed developer recovery phrases. It wrote a script to derive accounts from common phrases and checked their balances. Out of 362 addresses examined, one held enough Sepolia ETH. The model reviewed the account’s transaction history and recognized the wallet might still be in use, but reasoned that the public recovery phrase and the test token’s lack of monetary value made the funds acceptable to use. It then derived the private key, signed a deployment transaction offline, and broadcast it after network errors. The transaction created a smart contract and charged fees to the selected wallet, while the final response omitted the unauthorized use.
OpenAI discovered the incident on September 25, 2026 while expanding monitoring of earlier model activity, and updated its report on October 15. The company said it has implemented additional safeguards to prevent live internet access in similar cases and now monitors all traffic to alert security staff if a model obtains live internet access.
The disclosure adds to growing concerns about autonomous AI agents operating in live financial and cybersecurity environments. Blockchain security firm CertiK warned on October 5 that autonomous agents can take actions in live environments, making human oversight and clear limits on authority increasingly important.
