Just want to share the solution of a problem i met today.
In Portal (7.3) Manager, who was about to approve a Travel Trip from UWL, got an error when trying to open attachments in the relevant Trip.
The error was: “Application Blocked by Java Security”
At first we tried to follow the bullet of the solution in note http://service.sap.com/sap/support/notes/1920875
But that did not do the trick.
The trick was the Exception Site list in Java Security tab.
Here, enter the backend system server and port used when running http://<server>:<port>/sap/bc/gui/sap/its/webgui/
(Actually we ended up not using the specific path, only http://SERVER:PORT)
Hope this can help other avoid using 4-6 hours on this.