Brian Krebs reports:
Hospitality giant Hilton Hotels & Resorts recently started offering Hilton HHonors Awards members 1,000 free awards points to those who agreed to change their passwords for the online service prior to April 1, 2015, when the company said the change would become mandatory. Ironically, that same campaign led to the discovery of a simple yet powerful flaw in the site that let anyone hijack a Hilton Honors account just by knowing or guessing its valid 9-digit Hilton Honors account number.
[…]
After that, they could see and do everything available to the legitimate holder of that account, such as changing the account password; viewing past and upcoming travel; redeeming Hilton Honors points for travel or hotel reservations worldwide; or having the points sent as cash to prepaid credit cards or transferred to other Hilton Honors accounts. The vulnerability also exposed the customer’s email address, physical address and the last four digits of any credit card on file.
Read more on KrebsOnSecurity.com