In a statement on the company's website, the US-based business said they were asking users to reset their passwords after an attack "compromised a database containing encrypted passwords and other non-financial data".
The site, which has more than 14 million active users in the UK, was quick to say that it believes no unauthorised access was gained to personal data, but that a password reset was the best practice to help ensure security.
"Cyberattackers compromised a small number of employee log-in credentials, allowing unauthorised access to eBay's corporate network," said the statement.
"Working with law enforcement and leading security experts, the company is aggressively investigating the matter and applying the best forensics tools and practices to protect customers. Information security and customer data protection are of paramount importance to eBay Inc, and eBay regrets any inconvenience or concern that this password reset may cause our customers.
"We know our customers trust us with their information, and we take seriously our commitment to maintaining a safe, secure and trusted global marketplace."
eBay said that the database was breached at some point in late February and early March, with access gained to personal customer information including passwords, addresses and dates of birth.
"However, the company says that no financial information has been compromised as this data is stored on a separate database under a different encryption.
"The compromised employee log-in credentials were first detected about two weeks ago. Extensive forensics subsequently identified the compromised eBay database, resulting in the company's announcement today," said the statement.
"The company said it has seen no indication of increased fraudulent account activity on eBay. The company also said it has no evidence of unauthorised access or compromises to personal or financial information for PayPal users. PayPal data is stored separately on a secure network, and all PayPal financial information is encrypted."
The internet is still recovering from the Heartbleed bug, a flaw in the OpenSSL encryption on computers that protects user information when someone is online.
The flaw had been present for two years undetected, and offered hackers a way into personal accounts across the web. UK parental advice site Mumsnet was the first to admit they had been a victim of the bug. Fixes, or "patches", have since been applied across the web as sites recover from the bug.