Microsoft issued a patch for a vulnerability in Windows Print Spooler last month. But some security researchers spotted that Microsoft had reclassified the vulnerability as critical They released proof-of-concept code that exploited a remote code execution security hole in the software. The researchers realised their mistake and have now deleted their code. To mitigate this vulnerability, please update Windows to the latest version, or disable the PrintSpooler service on vulnerable PCs, and limit network access to servers where you feel you need to keep the Print Spools running.”]
Source: https://grahamcluley.com/printnightmare-zero-day-exploit/