FULL PRODUCT VERSION :
java version "1.8.0_60"
Java(TM) SE Runtime Environment (build 1.8.0_60-b27)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
OS X 10.10.5
OS X 10.9.3

A DESCRIPTION OF THE PROBLEM :
Showing a modal dialog from DropTargetListener.drop(DropTargetDropEvent) causes the UI to lock up.

This happens on an OS X 10.10.5 and an OS X 10.9.3 system that we tried, but not on one 10.7 system.

Problem did not happen on Java 8 update 51.

REGRESSION. Last worked in version 8u51

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile and run code.
Drag, for example, a file from Finder onto the window.
Attempt to "OK" the dialog that pops up.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
"OK" should close the dialog.
ACTUAL -
The dialog will not close. The UI is frozen.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.dnd.*;
import javax.swing.*;

public class DropTest {

   public static void main(String[] args) {
      SwingUtilities.invokeLater(
         new Runnable() {
            public void run() {
               launchGui();
            }
         });
   }
   
   public static void launchGui() {
      JFrame f = new JFrame();
      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      final JPanel c = new JPanel();
      f.getContentPane().add(c);
      new DropTarget(c,
         new DropTargetAdapter() {
            public void drop(final DropTargetDropEvent e) {
               JOptionPane.showMessageDialog(c, "Test");
            }
         });
      f.setSize(400, 400);
      f.setVisible(true);
   }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
From DropTargetListener.drop(), do anything that might show a modal dialog in SwingUtilities.invokeLater().