Verizon confirmed Wednesday that data belonging to 6 million customers was leaked online in June. News of the incident was first reported by ZDNet.

In a statement on the company's website, Verizon said the leak was caused by an employee of one of the company's vendors who accidentally allowed external access to information put in a cloud storage area. ZDNet reported that the data was leaked on an unprotected Amazon S3 storage server. This made the data available to anyone who had the public link to the cloud. (Amazon chief executive Jeffrey P. Bezos also owns The Washington Post.)

Amazon didn't respond to a request for comment.

A limited amount of personal information, such as some phone numbers and PINs, was included in the data, but it didn't include Social Security numbers or voice recordings, Verizon said. The PIN numbers are used to authenticate a caller phoning into the wireline call center and can't be used to access customer accounts online, the statement said.

No customer information was lost or stolen, because the storage area was accessible only to Verizon; the vendor, Israel-based NICE Systems; and the researcher who flagged the leak, according to the statement.

That researcher was Chris Vickery, who worked for the cybersecurity firm UpGuard. Vickery also discovered earlier this year that some information of nearly 200 million voters was exposed by a data firm working for Republican Party clients. That information was also on an Amazon server.

Vickery said he doesn't think the issues have anything to do with Amazon's product. It's more because they are the industry leader in cloud technology, which makes it inevitable that their name comes up when issues arise, he said. The issues stem more from the companies that use Amazon's products that "misconfigure" the cloud servers, which lead to issues like these, Vickery said.

"It’s more of a general concept of people using these cloud file repositories but not having the greatest knowledge of the consequences of various settings," he said.

Vickery said he alerted Verizon to the issue on June 13.  The security hole was sealed June 22.

Although Verizon said that the PINs alone can't help access online accounts, Hemu Nigam, a cybersecurity analyst at SSP Blue, said he would still advise customers to change their PINs because they could give people access to other accounts they use.

“The unfortunate part is if you use that PIN, you're probably using a similar PIN for other situations, so once I have that I can test that PIN on other things,” he said. “Verizon's relationship with the customer is not at risk, but the customer is now at risk in other aspects of their lives.”