One of the companies stored 146 gigabytes of data containing more than 540 million records, including comments, likes, responses, and account names, on the Amazon servers, according to UpGuard. The number of users whose data was included is not yet clear.
Another app is said to have stored unprotected Facebook passwords for 22,000 users.
Chris Vickery, director of cyber risk research at UpGuard, told CNN Business that the discovery "highlights a problem inherent to mass data collection."
Vickery said the data seemed to have been collected via Facebook integration. Facebook allows third-party developers to integrate apps and websites with the platform to allow functionality such as logging into a service using Facebook.
Facebook has "no way to guarantee secure storage of the data to their end users if they are to allow app developers to harvest it in bulk ," Vickery said.
In a statement given to CNN Business, a Facebook spokesman said: "Facebook's guidelines prohibit storing Facebook information in a public database. When we notified the problem, we worked with Amazon to take down the databases. We are committed. to work with the developers on our platform to protect people's data. "
Representatives of Amazon did not immediately respond to a request for comment.
Bloomberg was the first to report the news.
The new discovery is the latest to mark Facebook's struggle to protect the data collected from its over 2 billion users. It can only increase the control of the company after a year of data security scandals.
In March last year, it broke out that Cambridge Analytica, a data company affiliated with Donald Trump's presidential campaign, had access to information from as many as 87 million Facebook users without their knowledge.