Hi Jacob,
I'm Paul and I'm here to help you with your concern.
MicrosoftSecurityApp.exe is a legitimate file and I think it is part of the Microsoft Defender Store app.
https://www.microsoft.com/store/productid/9P6PM...
If you want you can remove it via Powershell.
> Open Powershell as Admin.
> Enter the command below.
get-appxpackage -allusers Microsoft.6365217CE6EB4 | remove-appxpackage
I hope this helps. Feel free to ask back any questions and keep me posted.