: Sending fake invoices to other users to trick them into "refunding" money to a scammer's account.
In the context of data leaks, "121x" usually indicates the or a specific batch identifier for the stolen data. These files are circulated on underground forums or "combolist" sites and are used by malicious actors for:
If you suspect your information might be in such a file, take immediate action: How to Report Suspicious Emails & Messages | PayPal US
: Using the personal information within the account to access other services. How to Protect Your Account
: Draining linked bank accounts or credit cards.