My first reaction was that
 it probably was a false alarm.  But then  I thought, that was the
 very first time EVER I saw that message when installing any program, even
 LibreCAD 2.1.3.  
Ah, it seems LibreCAD just
 doesn't have a certificate from Microsoft or something like that
 (unrecognized app). If you click on More info what happens then?
 Are you asked if you want to run it anyway? 
I think it's false alarm.
	
	
	
	
	
	
	
	
		
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NAML