An investigation has been launched after some customers using Lloyds, Halifax and Bank of Scotland apps were able to see other users' transactions on their accounts.
The glitch meant they were able to view charges and payments made by other people.
A spokesperson for Lloyds Banking Group - which owns all three banks - apologised for the issue and said the incident had been resolved.
It is unclear exactly how many users have been affected.
Outage tracking website Downdetector.com saw a spike in reports of issues with the Halifax and Lloyds apps between 07:00 and 09:00.
