(WJW) — The company formerly known as Square announced a customer information data breach on its mobile payment service Cash App.

Block Inc. filed a report with the Securities and Exchange Commission (SEC) Monday admitting to the breach, which took place on Dec. 10 and reportedly involved a former employee.

The records the employee, who was no longer working for the company at the time of the breach, was able to access included full names and brokerage account numbers (which have to do with stock activity), but not social security numbers or banking information.

It’s not currently known how many customers are directly affected by the incident, but it reportedly only impacted those in the U.S.

In the filing, the company said an investigation is currently underway:

The Company takes the security of information belonging to its customers very seriously and continues to review and strengthen administrative and technical safeguards to protect the information of its customers. Future costs associated with this incident are difficult to predict. Although the Company has not yet completed its investigation of the incident, based on its preliminary assessment and on the information currently known, the Company does not currently believe the incident will have a material impact on its business, operations, or financial results.

The company says its millions of users are going to be notified of the breach, so look out for an email. Those who have any questions regarding the incident can reach out to the company.

Cash App is a mobile payment service owned by Block, Inc. (which used to be called Square). Users can transfer money directly to other people (like with Venmo), and they can also use it to buy stocks and cryptocurrencies.