diff -r 4ebc2e2fb97c -r 71c04702a3d5 test/jdk/java/security/SignedObject/Correctness.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/security/SignedObject/Correctness.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 6618658
+ * @summary Deserialization allows creation of mutable SignedObject
+ */
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.security.KeyPair;
+import java.security.KeyPairGenerator;
+import java.security.Signature;
+import java.security.SignedObject;
+
+
+public class Correctness {
+
+    public static void main(String[] args) throws Exception {
+
+        String SIGALG = "SHA1withRSA";
+        KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
+        KeyPair kp = kpg.generateKeyPair();
+
+        SignedObject so1 = new SignedObject("Hello", kp.getPrivate(),
+                Signature.getInstance(SIGALG));
+
+        ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
+        ObjectOutputStream out = new ObjectOutputStream(byteOut);
+        out.writeObject(so1);
+        out.close();
+
+        byte[] data = byteOut.toByteArray();
+
+        SignedObject so2 = (SignedObject)new ObjectInputStream(
+                new ByteArrayInputStream(data)).readObject();
+
+        if (!so2.getObject().equals("Hello")) {
+            throw new Exception("Content changed");
+        }
+        if (!so2.getAlgorithm().equals(SIGALG)) {
+            throw new Exception("Signature algorithm unknown");
+        }
+        if (!so2.verify(kp.getPublic(), Signature.getInstance(SIGALG))) {
+            throw new Exception("Not verified");
+        }
+    }
+}