A serious flaw has been found in Apple's macOS operating system

Apple iMac and MacBook owners are being warned about a serious flaw which allows anyone to access their machine's most important data without the need for a password.

The bug, which was discovered by Turkish developer Lemi Ergin, gives powerful administrator rights via a very simple hack.

Why this is so serious is that, once entry at this level has been gained, it allows anyone to delete crucial system files, change administrator passwords and add or remove system accounts.

Mr Egin says he discovered the flaw by simply entering the username "root" and leaving the password blank in the system admin settings.

After a few attempts he gained full administrator access to the Mac.

Express.co.uk has tried the hack and can confirm that it does work.