Update Release notes etc.

Author: khmarbaise

README.md

@@ -7,6 +7,11 @@ Plexus-archiver
 
 The current master is now at https://github.com/codehaus-plexus/plexus-archiver
 
+## Important Hint
+
+Based on a hint of Sync.io Security Team we have integrated a patch for solving 
+a possible security issue.
+
 ## Release Notes
 
 You can find details about the different releases in the [Release Notes](https://github.com/codehaus-plexus/plexus-archiver/blob/master/ReleaseNotes.md).