src/java.desktop/macosx/classes/sun/lwawt/macosx/LWCToolkit.java

@@ -188,14 +188,20 @@
      * If false we operate in singleThreaded FX/AWT interop mode and nested loop uses NSDefaultRunLoopMode
      */
     private static final boolean inAWT;
 
     public LWCToolkit() {
-        areExtraMouseButtonsEnabled = Boolean.parseBoolean(System.getProperty("sun.awt.enableExtraMouseButtons", "true"));
+        final String extraButtons = "sun.awt.enableExtraMouseButtons";
+        AccessController.doPrivileged((PrivilegedAction<Void>) () -> {
+            areExtraMouseButtonsEnabled =
+                 Boolean.parseBoolean(System.getProperty(extraButtons, "true"));
         //set system property if not yet assigned
-        System.setProperty("sun.awt.enableExtraMouseButtons", ""+areExtraMouseButtonsEnabled);
-        initAppkit(ThreadGroupUtils.getRootThreadGroup(), GraphicsEnvironment.isHeadless());
+            System.setProperty(extraButtons, ""+areExtraMouseButtonsEnabled);
+            initAppkit(ThreadGroupUtils.getRootThreadGroup(),
+                       GraphicsEnvironment.isHeadless());
+            return null;
+        });
     }
 
     /*
      * System colors with default initial values, overwritten by toolkit if system values differ and are available.
      */