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.

In what’s one of the more significant series of cyberattacks in 2025, hackers are targeting a severe weakness in Microsoft’s Sharepoint software, which is used by its customers to build and manage shared files. Among the attackers, according to Google security researchers, is a Chinese-affiliated group.