CME Group says that a software bug at its swaps data repository earlier this month allowed some traders to see confidential details on hundreds of transactions.
Last year, as a result of Dodd-Frank, the Commodity Futures Trading Commission (CFTC) outlined plans for new rules requiring all swaps trades to be reported to trade-data repositories.
Under the regulations, traders can access data such as prices and volumes on transactions but not the identity of the participants involved.
However, according to a Wall Street Journal report, a bungled software upgrade at CME Group's repository meant that on 1 April some traders could see details on who had traded with whom in around 500 transactions tied to agriculture and energy prices.
Customers alerted the CME the following day of the issue, which affected a tiny percentage of the one million transactions carried out during the problem.
"We regret this incident occurred, as maintaining the confidentiality of market participant data at all times is vital to the operation of our markets and systems," says CME Group in a statement.
CME admits data leak - WSJ