It outputs an error log.
Whoops! An error occurred. Unfortunately, this error was not recoverable :(. Firefly III broke. The error is:
Could not save preference: SQLSTATE[22001]: String data, right truncated: 1406 Data too long for column 'data' at row 1 (SQL: update `preferences` set `data` = [{"ip":"00.000.00.00","time":"2022-05-30 20:02:06","notified":false},{"ip":"00.000.00.00","time":"2022-05-30 20:02:10","notified":false},{"ip":"00.000.00.00","time":"2022-05-30 20:02:15","notified":false},{"ip":"00.000.00.00","time":"2022-05-30 20:02:16","notified":false}, ...
My IP was in the list.
Let's just say it is hard to trust a piece of software with my financial data after this.
(I changed all the IP addresses for 00.000.00.00 to preserve some anonymity.)