An Ex-Employee Is Behind the Cash App Breach Impacting Over 8 Million Users. Here's Everything We Know So Far. According to the company's SEC filing, the former employee downloaded reports containing U.S. customer data on December 10.

Block Inc. confirmed Monday that a security breach initiated by a former employee several months ago has potentially impacted 8.2 million users of Cash App, the mobile-payment service that facilitates the transfer of funds, and, more recently, the purchase of stocks and Bitcoin. According to the company's SEC filing, the ex-employee downloaded reports containing U.S. customer data on December 10.

The filing also reveals that only customers who used the app's stock-related features were affected by the breach. The reports in question included customers' full names and brokerage account numbers, and in some cases, also included brokerage portfolio value, brokerage portfolio holdings and/or stock trading activity. They didn't include usernames or passwords, Social Security numbers, dates of birth, payment-card information, addresses, bank-account information or any other personally identifiable information.

Related: The How-To: Protect Your Business From a Data Breach

At one point, the ex-employee "had regular access to these reports as part of their past job responsibilities," the filing states, but their employment had already come to an end when the download occurred. Block declined to answer TechCrunch's questions as to why a former employee was still able to access the reports, and for what length of time they continued to have access following their employment's end.

"At Cash App we value customer trust and are committed to the security of customers' information," Cash App spokesperson Danika Owsley told TechCrunch in a statement. "Upon discovery, we took steps to remediate this issue and launched an investigation with the help of a leading forensics firm. We know how these reports were accessed, and we have notified law enforcement. In addition, we continue to review and strengthen administrative and technical safeguards to protect information."

Block's investigation of the incident is ongoing.

Related: 8 Ways a Data Breach Could Take Out Your Company Tomorrow

Block, formerly known as Square, is also behind numerous other enterprises, including music-streaming service Tidal and Bitcoin company Spiral.

Block, Inc. was down more than 7% as of 10:12 a.m. ET.