If you want someone else to be able to run your script app, you’ll need to sign it and get it past Gatekeeper’s checks. Here are more details about the role of xattrs in those, and how to run a full check without downloading your app.
They’re responsible for determining Gatekeeper’s checks, contain Finder information, and much more. With a new free tool too.
Perhaps not as effective as one of the better anti-virus apps, it is free and built into OS X.