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.

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.

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

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,

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

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.