Hackers stole Meta employee account credentials, broke into parts of the company’s GitHub repositories and made off with product source code and personal data on about 1,500 people, SecurityWeek reported on Oct. 13. Most of the victims are Meta employees in the United States.

Meta confirmed the intrusion and notified victims, the report said.

Meta said 99 percent of the data taken by the attackers was software code for some products, while the remaining 1 percent was personal information.

The personal data should not have been on GitHub in the first place. Meta said it was uploaded to the repositories by mistake, in violation of company policy. It added that much of the data that appeared to be personal information was synthetic or anonymised test data. Meta said that would make it difficult for attackers to distinguish real records from fake ones.

Meta said an external organisation stole the account credentials of 1 employee and used them to break in. It did not disclose how the credentials were leaked.

A Meta spokesperson said Meta’s internal systems were not compromised.

Meta did not say what kinds of personal information were exposed, how many repositories were breached or who the attackers were. It also did not disclose when the intrusion began.