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.

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

The company said state-backed hacking groups were breaching systems through flaws in SharePoint, which is used by the U.S. government and companies around the world.