The backdoor-like vulnerability was discovered through the Windows Defender ATP kernel sensors back in January, but Microsoft did not alert the media. Instead, the company contacted Huawei directly and a patch was promptly released. Microsoft presumably did not want to add to the list of serious allegation currently targeting Huawei.
https://www.notebookcheck.net/Microsoft-spots-critical-flaw-in-Huawei-s-Matebook-device-manager-driver.415176.0.html