At least two Chinese hacking groups were using security flaws in SharePoint, a popular collaboration software, to breach systems, Microsoft said.

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

Microsoft said in a post on its website on Saturday that it was “aware of active attacks targeting on-premises SharePoint Server customers by exploiting vulnerabilities.” SharePoint is a Microsoft platform that allows customers to manage and share documents within their organizations.