No idea. It is probably some kind of file attribute or something that web browsers do to mark files as downloaded from the internet or whatever unsafe place they thing they are coming from. 
Yes, I know that attribute well and I see it for executables. But just not for C- (Text-) files. I wonder why it is there??? I also don't see it if I download a C- (Text-) file file from a cloud folder. I have seriously no clue how to do that.
I guess I'll need to take a look into Win-API so see if I can write a tool that sets this attribute for any file... WTF...
