US online giant eBay says the number of users potentially affected by a massive data breach could be as many as 145 million.
"All eBay users are being asked to change their password," a spokeswoman said in an email on Thursday.
"At the end of the first quarter, we had 145 million active buyers."
The number is higher than the 128 million active users cited on the eBay website.
The company disclosed on Wednesday that cyber attackers broke into its database containing customer passwords and other personal data in what could be one of the biggest breaches of its kind.
An eBay statement said the database was compromised between late February and early March and "included eBay customers' name, encrypted password, email address, physical address, phone number and date of birth".
But it added that it "did not contain financial information or other confidential personal information".
The attack did not affect data from PayPal, the finance and payments unit of the company.
