-- Apple said it is aware of "intermittent" attacks on iCloud users and is urging users to take precautions to make sure their private information stays safe.
The new security bulletin comes as reports have emerged that some iCloud users in China have been diverted to unauthorized websites when they attempt to sign into their accounts.
"We're aware of intermittent organized network attacks using insecure certificates to obtain user information, and we take this very seriously," the bulletin said.
The hacking attempts don't impact users who sign in to their iCloud accounts on iOS devices. Macs running the new OS X Yosemite using Safari are also not impacted, Apple said.
The company recommends users protect their data by making sure they have a secure connection to iCloud.com before entering any personal information.
"If users get an invalid certificate warning in their browser while visiting www.icloud.com, they should pay attention to the warning and not proceed," Apple said in the post.
The Associated Press contributed to this report.