The personal information of Facebook users has been exposed on the internet via Amazon’s cloud computing servers, researchers said on Wednesday, in the latest revelation to stoke fears over user privacy on the social network.

Cybersecurity firm UpGuard said in a blog post that it had discovered two large sets of data harvested from Facebook users by third-party apps that used Amazon Web Services to run their business. It is unclear how long that data — which included account names, email addresses and comments posted on Facebook — had been exposed for, UpGuard said.

The discovery shows that a year after the Cambridge Analytica scandal exposed how unsecure and widely disseminated Facebook users’ information is online, companies that control that information at every step still haven’t done enough to seal up private data.

In one instance, Mexico City-based digital platform Cultura Colectiva, openly stored 540 million records on Facebook users, including identification numbers, comments, reactions and account names. The records were accessible and downloadable for anyone who could find them online. That database was closed on Wednesday after Bloomberg alerted Facebook to the problem and Facebook contacted Amazon. Facebook shares pared their gains after the Bloomberg News report.

Another database for a long-defunct app called At the Pool listed names, passwords and email addresses for 22,000 people. UpGuard doesn’t know how long they were exposed, as the database became inaccessible while the company was looking into it.

Facebook Inc. shared this kind of information freely with third-party developers for years, before cracking down more recently. The problem of accidental public storage could be more extensive than those two instances. UpGuard found 100,000 open Amazon-hosted databases for various types of data, some of which it expects aren’t supposed to be public.

“The public doesn’t realize yet that these high-level systems administrators and developers, the people that are custodians of this data, they are being either risky or lazy or cutting corners,” said Chris Vickery, director of cyber risk research at UpGuard. “Not enough care is being put into the security side of big data.”

Cultura Colectiva is a digital platform that posts stories about celebrities and culture and largely targets a Latin American audience. The company’s website says it creates content through data and technology and has more than 45 million followers on Facebook, Instagram, Twitter, YouTube and Pinterest.

Facebook for many years allowed anyone making an app on its site to obtain information on the people using the app, and those users’ friends. Once the data is out of Facebook’s hands, the developers can do whatever they want with it.

Last year, Facebook started an audit of thousands of apps and suspended hundreds until they could make sure they weren’t mishandling user data. Facebook now offers rewards for researchers who find problems with its third-party apps.

A Facebook spokesperson said that the company’s policies prohibit storing Facebook information in a public database. Once it was alerted to the issue, Facebook worked with Amazon to take down the databases, the spokesperson said, adding that Facebook is committed to working with the developers on its platform to protect people’s data.