I started a local webserver listening on localhost:80 just to see what happens, but this thing seems to not detect it. It shows me "Scanning localhost ... localhost complete."
Edit: My guess is that this thing can only detect servers that send a CORS header that permits cross domain access.
It could probably do way better detection if it did not do xhr requests but added script/css/whatever elements to its own page pointing to localhost and detects if those error out.
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