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.

Microsoft contained a major SharePoint security flaw, amid fresh questions about the future of its legacy on-premises software.

Microsoft has released security patches for the zero-day vulnerability chain dubbed ToolShell, capable of remote code execution on SharePoint, resulting in the exploitation of at least 54 organizations worldwide.

New estimates regarding the recently-exploited Microsoft SharePoint vulnerabilities now evaluate that as many as 400 organizations may have been targeted.

Microsoft confirms Chinese hackers exploited a SharePoint flaw; Patches now available. Cloud-based Microsoft 365 not affected.

Microsoft is issuing an emergency fix to close off a vulnerability in Microsoft’s SharePoint software that hackers have exploited to carry out widespread attacks on businesses and at least some federal agencies.

A security patch Microsoft (MSFT.O), opens new tab released this month failed to fully fix a critical flaw in the U.S. tech giant's SharePoint server software, opening the door to a sweeping global cyber espionage effort,

The SharePoint vulnerabilities that Microsoft released emergency patches for earlier this week – tracked as CVE-2025-53770 and CVE-2025-53771 – have been exploited much further than previously thought. As reported by Bloomberg, the number of companies and organizations affected by the two exploits has grown to more than 400 in just a few days.

DOD CIO says she's been speaking daily with Microsoft since the zero-day Sharepoint vulnerability was discovered.