The company has been called out repeatedly for inadequate security practices, and now we have another case in point: a successful SharePoint hack that’s among the worst in Microsoft’s history.

Multiple hacking groups—including state actors from China—have targeted a vulnerability in older, on-premises versions of the file-sharing tool after a flawed attempt to patch it.

Threat actors exploit SharePoint flaws to access internal systems, steal sensitive data, and carry out surveillance, impersonation, and extortion.