Apple is reporting some of its company computers were hacked on Tuesday and is laying the blame with an Internet plug-in called Java. U.S. Homeland Security officials warned earlier this year that Java software could be vulnerable to attacks.

“We are very familiar with business computers being breached, but those are all Windows machines,” says Jim Finkle, who covers cybersecurity for Reuters. “This is the most significant breach of Macintosh computers at a corporation.”

Apple says there is no evidence any data was taken during the attack, which is believed to have been carried out by the same group that recently breached Facebook’s computers.