Microsoft is urging customers who run Windows on a PC to update it immediately due to the threat of "print nightmare."
According to Microsoft, a guide was published accidentally, and hackers could use it to install programs, delete data, and create new user accounts with full access to a PC.
According to The Verge, the attack was so severe that Microsoft has to issue a patch for the 12-year-old Windows 7 more than a year after ending support for it.
"Microsoft has completed the investigation and has released security updates to address this vulnerability," the company said.
If you cannot install the updates, Microsoft says that consumers see their FAQ and Workaround sections.