If you are using Windows Defender be extra cautious, and make sure you install the fix Microsoft released for a newly discovered vulnerability if you aren't using the default Defender configuration. Attackers can use the vulnerability to take control of your computer by sending emails to you, and you don't even need to open an attachment to get compromised.
https://technet.microsoft.com/en-us/library/security/4022344.aspxGoogle says the vulnerability is the most severe possible in Windows.
https://bugs.chromium.org/p/project-zero/issues/detail?id=1252&desc=5On workstations, attackers can access mpengine by sending emails to users (reading the email or opening attachments is not necessary), visiting links in a web browser, instant messaging and so on.
Vulnerabilities in MsMpEng are among the most severe possible in Windows, due to the privilege, accessibility, and ubiquity of the service.
https://www.ghacks.net/2017/05/09/windows-defender-vulnerability-discovered-and-fixed/