Hackers have been dangling their 'phishing' rods over the European Nintendo website and the Epic Games website.
Both companies explicitly state that credit card information is safe.
"We have learnt of a possible phishing threat to users of the European Nintendo website which we are currently investigating," Nintendo Europe notified.
"The protection of our customers is our utmost priority and so we have taken the precaution of immediately shutting down some parts of this website until further notice.
"We would like to reassure you that we do not hold our customer's bank, credit card or address details on the European Nintendo website and so this data is not at risk."
Epic Games responded via a forum message posted on behalf of studio CEO Tim Sweeney.
"Our Epic Games web sites and forums were recently hacked," admitted Sweeney. "We're working on getting them back up and running and expect everything to be restored in a few days.
"The hackers likely obtained the email addresses and encrypted passwords of forum users. Plain text passwords weren't revealed, but short or common passwords could be obtained by brute-force attack. Therefore, we're resetting all passwords.
"The Unreal Developer Network (UDN) has not been compromised," added Sweeney. "None of our web sites ask for, or store, credit card information or other sensitive customer data."
Last week, Codemasters admitted suffering a hacker intrusion. Credit card information was not compromised, Codemasters explained in an open letter to customers.