Radisson Rewards members’ first names and last four digits of the 16-digit members number were sent to the wrong members. The company says that its network has not been compromised, and that accounts have not been accessed by unauthorised parties. Radisson says that it identified the issue on 23 May, and immediately halted all email communications while it investigated more deeply. Last October, the company discovered that personal information about members, including their names, physical addresses, countries of residence, email addresses, company names, telephone numbers, and frequent flyer numbers were accessed by hackers.”]
Source: https://grahamcluley.com/radisson-rewards-may-have-leaked-your-data-again/