SYDNEY — Australian airline Qantas said Sunday that data from 5.7 million customers stolen in a major cyberattack this year had been shared online, part of a leak affecting dozens of firms.

Disney, Google, IKEA, Toyota, McDonalds and fellow airlines Air France and KLM are also reported to have had data stolen in a cyberattack targeting software firm Salesforce, with the information now being held to ransom.

Salesforce said this month that it was “aware of recent extortion attempts by threat actors”.

Qantas confirmed in July that hackers had targeted one of its customer contact centres, breaching a computer system used by a third party now known to have been Salesforce.

They secured access to sensitive information such as customer names, email addresses, phone numbers and birthdays, the blue-chip Australian company said.

Credit card details and passport numbers were not kept in the system, Qantas stressed at the time.

No further breaches have taken place since and the company is cooperating with Australian security services.

“Qantas is one of a number of companies globally that has had data released by cyber criminals following the airline’s cyber incident in early July, where customer data was stolen via a third party platform,” the company said in a statement.

“With the help of specialist cyber security experts, we are investigating what data was part of the release,” it added.

It also said it had obtained a legal injunction with the Supreme Court of New South Wales, where the firm is headquartered, “to prevent the stolen data being accessed, viewed, released, used, transmitted or published by anyone, including third parties”.