Facebook has since announced that it would notify all users whose data was misused by British research firm Cambridge Analytica or any app developers who are found to have mismanaged users' personal information.
This addresses the issue of user information being sold to advertisers, research firms and the like, but it doesn't touch upon one of the internet's busiest marketplaces -- the dark web.
For the study, Fractl scoured all the fraud-related listings on the three biggest dark web marketplaces -- Dream, Point and Wall Street Market -- last month, according to MarketWatch.
To do this, they downloaded a Tor client, or a network that grants anonymity to internet browsers, which is required in order to access the dark web.
There, they discovered that Facebook logins are sold for just US$5.20 ($7.18) each.
Obtaining someone's Facebook credentials can serve as a gateway into hundreds of other apps they've also granted access.
That's because Facebook allows thousands of third-party "vampire apps" to plug in to its social network and siphon off data from its users.
This means anything from popular services like Airbnb and Spotify, to dodgy quiz apps or online games like Farmville.
Many users may use their Facebook account to login to these apps, which means that if a hacker has your credentials for the social media platform, they can easily get into many other accounts.
Meanwhile, credentials for other popular services like Gmail, Uber and Grubhub are just as cheap.
Your Gmail username and password is a bargain at just US$1, while Uber account logins go for US$7 and Grubhub logins sell for US$9.
By comparison, the most expensive logins are for PayPal, which can demand up to US$247, according to Fractl.
According to experts, the reason why some credentials sell for cheap is because hackers can so easily obtain it nowadays.
It's a classic case of supply and demand: With so much data available on the internet, hackers can easily obtain it, sell it and move on.
Similarly, a separate study by security research firm Top 10 VPN revealed that your entire online identity can be sold for approximately US$1,200.
Top 10 VPN also found that Facebook logins would sell for US$5.20 on the dark web.
What's perhaps most concerning is that the firm found that extremely sensitive 'proofs of identity' like passports and selfies or utility bills sell for US$62 and US$29, respectively.
According to Top 10 VPN, criminals can purchase online banking details for just US$160, while all of your financial information can sell for US$710.
The firm found that hacked financial details were "by far" the most commonly listed items, with credit cards being the most valuable.
PayPal accounts were also in high demand, Top 10 VPN noted.
Interestingly, they discovered that other popular listings are often referred to as "fullz."
"These bundles of 'full' identifying information, sometimes are either packaged with financial details or sold separately," the firm said.
"We found listings featuring individuals' name, billing address, mother's maiden name, social security number, date of birth and other personal data."
The items that garnered the lowest price tag were online dating logins for sites like Match.com or Plenty of Fish.
"While hacked dating accounts could certainly be used for 'castfishing,'...it's cheaper and easier to just create fake accounts," the firm noted.
