Researcher discovers Venmo exposes 'an alarming amount' of personal data in public API

Next time you make a payment on Venmo, beware: almost anyone can track it.

The popular mobile payments app is sharing users' personal data — including real names, comments sent with the payment, transaction dates, and recipients of the transaction — with the public by default. This information is being exposed through company’s public API, and it can be hidden by adjusting your privacy settings from "Public" to "Private."

Security researcher Hang Do Thi Duc recently discovered this "alarming amount" of information being leaked by examining the public API. The reason its happening, the researcher suggests, is because the Venmo app's default settings are set to "Public" for all users.

Using transaction data made available through the public API, Do Thi Duc downloaded 207,984,218 Venmo transactions, all the public transaction made on the app in 2017, and analyzed them. She has detailed her findings in an aptly named project called Public By Default.

To show just how much detail you can pull from the public Venmo transaction data, Do Thi Duc’s Public By Default project focuses on on five specific Venmo accounts. The five accounts, whose identities she’s chosen to keep private, include a Cannabis seller in California, a food truck vendor, a married man and woman, a junk food lover, and a fighting couple.

The amount of information Do Thi Duc is able to pull from the transaction data Venmo is sharing is pretty astonishing. For example, she was able to track the food truck vendor’s number one customer and find exactly when she’d go and what she was buying to eat. In the case of the married couple, Do Thi Duc was able to not only tell where they shop but also who was responsible for what bill.

In her report, Do Thi Duc was able to obtain even more information about the people behind these public transactions based on the profile picture they were using. If a Venmo user chose to link up their Facebook account so they can use the same profile picture as their Venmo avatar, Venmo’s public API shares the Facebook picture URL along with the rest of the transaction. This profile picture URL includes a user’s Facebook ID, which in turn will direct you straight to a person Facebook profile.

The fact that Venmo has enabled such easy access to this type of information in the form of a public API is problematic. In the hands of the right – or wrong – person this info is ripe for identity theft. Not only that, but the access to this information by say a stalker or domestic abuser is potentially dangerous.

In a statement, Venmo is quick to point out that while the “safety and privacy of Venmo users and their information is one of our highest priorities,” when it comes to protecting this information, it’s up to each Venmo user to change their default Venmo settings and make it private.

We recommend you do just that.