I am using a WebView in a JFXPanel in a Sandboxed JApplet.
Whenever i scroll inside the WebView these two exceptions are thrown.
The exception is caught in the JavaFX source and logged, thus the subsequent code still works.

Also, when trying to scroll by dragging the scrollbar thumb, many more of these exceptions are thrown and the view is not updated at all.

java.security.AccessControlException: access denied ("java.lang.reflect.ReflectPermission" "suppressAccessChecks")
at java.security.AccessControlContext.checkPermission(Unknown Source)
at java.security.AccessController.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkPermission(Unknown Source)
at sun.plugin2.applet.AWTAppletSecurityManager.checkPermission(Unknown Source)
at java.lang.reflect.AccessibleObject.setAccessible(Unknown Source)
at com.sun.javafx.webkit.theme.ScrollBarThemeImpl.getFieldValue(Unknown Source)
at com.sun.javafx.webkit.theme.ScrollBarThemeImpl.getThumb(Unknown Source)
at com.sun.javafx.webkit.theme.ScrollBarThemeImpl.thumbPosition(Unknown Source)
at com.sun.javafx.webkit.theme.ScrollBarThemeImpl.getThumbPosition(Unknown Source)
at com.sun.webkit.WebPage.twkProcessMouseWheelEvent(Native Method)
at com.sun.webkit.WebPage.dispatchMouseWheelEvent(Unknown Source)
at javafx.scene.web.WebView.processScrollEvent(Unknown Source)
at javafx.scene.web.WebView.lambda$registerEventHandlers$33(Unknown Source)
at javafx.scene.web.WebView$$Lambda$94/15498521.handle(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
at javafx.event.Event.fireEvent(Unknown Source)
at javafx.scene.Scene.processGestureEvent(Unknown Source)
at javafx.scene.Scene.access$300(Unknown Source)
at javafx.scene.Scene$ScenePeerListener.scrollEvent(Unknown Source)
at com.sun.javafx.tk.quantum.EmbeddedScene.lambda$null$281(Unknown Source)
at com.sun.javafx.tk.quantum.EmbeddedScene$$Lambda$181/8594143.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.EmbeddedScene.lambda$mouseEvent$282(Unknown Source)
at com.sun.javafx.tk.quantum.EmbeddedScene$$Lambda$180/17817549.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$164(Unknown Source)
at com.sun.javafx.application.PlatformImpl$$Lambda$63/6407488.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$165(Unknown Source)
at com.sun.javafx.application.PlatformImpl$$Lambda$61/26289612.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$141(Unknown Source)
at com.sun.glass.ui.win.WinApplication$$Lambda$54/11261627.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

java.lang.NullPointerException
at com.sun.javafx.webkit.theme.ScrollBarThemeImpl.thumbPosition(Unknown Source)
at com.sun.javafx.webkit.theme.ScrollBarThemeImpl.getThumbPosition(Unknown Source)
at com.sun.webkit.WebPage.twkProcessMouseWheelEvent(Native Method)
at com.sun.webkit.WebPage.dispatchMouseWheelEvent(Unknown Source)
at javafx.scene.web.WebView.processScrollEvent(Unknown Source)
at javafx.scene.web.WebView.lambda$registerEventHandlers$33(Unknown Source)
at javafx.scene.web.WebView$$Lambda$94/15498521.handle(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
at javafx.event.Event.fireEvent(Unknown Source)
at javafx.scene.Scene.processGestureEvent(Unknown Source)
at javafx.scene.Scene.access$300(Unknown Source)
at javafx.scene.Scene$ScenePeerListener.scrollEvent(Unknown Source)
at com.sun.javafx.tk.quantum.EmbeddedScene.lambda$null$281(Unknown Source)
at com.sun.javafx.tk.quantum.EmbeddedScene$$Lambda$181/8594143.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.EmbeddedScene.lambda$mouseEvent$282(Unknown Source)
at com.sun.javafx.tk.quantum.EmbeddedScene$$Lambda$180/17817549.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$164(Unknown Source)
at com.sun.javafx.application.PlatformImpl$$Lambda$63/6407488.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$165(Unknown Source)
at com.sun.javafx.application.PlatformImpl$$Lambda$61/26289612.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$141(Unknown Source)
at com.sun.glass.ui.win.WinApplication$$Lambda$54/11261627.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)