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.

It issued an alert about “active attacks” targeting its server software and urged customers to install new security updates that have been released.

The attacks, discovered over the weekend, exploit a previously unknown vulnerability in the document-sharing software, prompting immediate action from both Microsoft and federal investigators. Newsweek reached out to Microsoft and the Cybersecurity and Infrastructure Security Agency (CISA) via email for comment.

Microsoft has issued an alert about "active attacks" on server software used by government agencies and businesses to share documents within organizations, and recommended security updates that customers should apply immediately.

Microsoft warns of hackers exploiting SharePoint vulnerabilities to breach critical organizations, including U.S. nuclear security.

Hackers are exploiting a flaw in a commonly used Microsoft program to gain access to passwords, sensitive data and more.

Hackers exploited a major security flaw in widely used Microsoft server software to launch a global attack on government agencies and businesses in the pas