A program to share information with cybersecurity companies may have exposed unpatched flaws in the company’s SharePoint service.

Microsoft is investigating whether a leak from its early alert system for cybersecurity companies allowed Chinese hackers to exploit flaws in its SharePoint service before they were patched, Bloomberg News reported on Friday.

Last year, the Department of Homeland Security released a scathing report detailing Microsoft’s mistakes during a 2023 hack in which China stole thousands of emails from top government officials. Two years before that, China-linked cyberattackers compromised more than 250,000 Microsoft Exchange servers.