Freedom Mobile says the data of about 15,000 customers was exposed by a security breach that began in late March.

The wireless service arm of Shaw Communications Inc. says it was alerted to the problem on April 18 by outside security researchers and the breach was closed by Freedom’s third-party service providers on April 23.

Freedom says a “very limited amount” of customer data was exposed as a result of a misconfigured server.

It says there’s no evidence that any customer data has been misused but it’s still conducting an investigation to determine the full impact of the breach.

Freedom also says it’s contacting affected customers about the breach.

The wireless carrier was apparently warned of the breach by researchers at vpnMentor, which announced it to the press.