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.

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

Federal cybersecurity officials have issued a warning to Microsoft users about a security flaw allowing hackers to access to certain SharePoint systems.

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

Victims of the recent global hacking campaign include the National Institutes of Health and the National Nuclear Security Administration, officials said.

Investors are desensitized to cyberattacks and have other issues on their mind ahead of Microsoft’s earnings report next week, analysts say.