src/java.desktop/unix/classes/sun/awt/X11/XToolkit.java

@@ -344,14 +344,18 @@
             AwtScreenData defaultScreen = new AwtScreenData(XToolkit.getDefaultScreenData());
             awt_defaultFg = defaultScreen.get_blackpixel();
 
             arrowCursor = XlibWrapper.XCreateFontCursor(XToolkit.getDisplay(),
                 XCursorFontConstants.XC_arrow);
-            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);
-
+                System.setProperty(extraButtons, ""+areExtraMouseButtonsEnabled);
+                return null;
+            });
             // Detect display mode changes
             XlibWrapper.XSelectInput(XToolkit.getDisplay(), XToolkit.getDefaultRootWindow(), XConstants.StructureNotifyMask);
             XToolkit.addEventDispatcher(XToolkit.getDefaultRootWindow(), new XEventDispatcher() {
                 @Override
                 public void dispatchEvent(XEvent ev) {