Cruise giant Cunard is trying to allay concerns amongst customers after an email was sent containing confidential details of some 1,200 passengers.
The problem first came to light last Friday (22 June) when the cruise operator emailed customers on its database.
Unfortunately some recipients noticed that the email had an Excel spreadsheet attached, carrying the personal details of 1,225 passengers.
The spreadsheet included email addresses, telephone contact details and, probably most seriously, passport numbers of passengers, a forum user on CruiseCritic says.
Cunard has denied any passport details were included in the details.
It is unknown how many recipients were sent the spreadsheet.
Cunard moved quickly to calm passengers after word leaked out about the security mess-up, with many passengers contacted again and advised to change their booking numbers immediately via the operator's online trip management system.
An official admits, via a statement forwarded today, an "email was sent in error to some guests containing details relating to other guests' bookings".

"We took swift action to close down the check -in system, Voyage Personaliser, until we were able to re-issue new secure log-in details to affected guests. Email addresses for some guests were included in the information sent in error.
"We apologise and would like to reassure guests that the issue has been dealt with and we are in the process of contacting relevant guests with a new, secure log-in."
NB:Cunard ship image via Shutterstock.