The security flaw, known as PrintNightmare, affects the Windows Print Spooler service. Researchers at cybersecurity company Sangfor accidentally published a how-to guide for exploiting it.
The researchers tweeted in late May that they had found vulnerabilities in Print Spooler, which allows multiple users to access a printer. They published a proof-of-concept online by mistake and subsequently deleted it — but not before it was published elsewhere online, including developer site GitHub.
“We recommend that you install these updates immediately,” the company said.
If there’s any good news is that the current security update is cumulative, meaning it contains previous fixes for previous security issues too.
Update: This story has been updated to note that Microsoft has released a patch for Windows 11.