ADDITIONAL SYSTEM INFORMATION :
Microsoft Windows [Version 6.3.9600]

java version "1.8.0_172"
Java(TM) SE Runtime Environment (build 1.8.0_172-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.172-b11, mixed mode)

A DESCRIPTION OF THE PROBLEM :
When having a host object (JSObject implementation) in the global scope, and calling it like a function (without an owner), the global scope object is erroneously passed as an argument to the JSObject's call(Object,Object[]) method as the first argument.

This is regardless of strict mode: it happens either way.

Extra information: my guess would be that this is a result of changes made for JDK-8170565

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the supplied code. 

Uncomment the "use strict" line to see that this happens regardless of strict mode.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The following output:
undefined
ACTUAL -
The following output:
[object global]

---------- BEGIN SOURCE ----------
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import jdk.nashorn.api.scripting.AbstractJSObject;
import jdk.nashorn.api.scripting.JSObject;
import jdk.nashorn.api.scripting.NashornScriptEngineFactory;

public class A {

    public static void main(String[] args) throws Exception {
        ScriptEngine se = ((NashornScriptEngineFactory) new ScriptEngineManager()
                .getEngineFactories()
                .get(0))
                .getScriptEngine( //
                //                        "-strict"
                );

        JSObject o = (JSObject) se.eval("var a = ({}); a;");
        o.setMember("something", new AbstractJSObject() {
            @Override
            public Object call(Object thiz, Object... args) {
                System.out.println(thiz);
                return null;
            }

        });
        se.eval("var b = a.something; b();");
    }

}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
There is no workaround.

FREQUENCY : always