Mac users have been warned of the first worm that can automatically download ‘adware’ to their machines.

It comes just days after a second warning over firmware hacks was revealed – although Apple has already developed a fix.

The new privilege-escalation bug stems from new error-logging features that Apple added to OS X 10.10, the latest version of its Mac software.

It was first revealed last week, but was believed to be theoretical.

Now researchers say the first use of the technique has been spotted in the wild.

Researchers from anti-malware firm Malwarebytes said a new malicious installer is exploiting the vulnerability to surreptitiously infect Macs with several types of adware including VSearch, a variant of the Genieo package, and the MacKeeper junkware.

Last month, Stefan Esser blogged about a zero-day vulnerability in OS X, without having informed Apple about the problem first.

Read the full story at Daily Mail.