File attachment having % in their file name are not allowed

Steps:.
1. Launch JIRA 4.0(QA build 159)
2. Create an issue and try to attach a file having % or $ in its file name.

Results:
1. It give error message of invalid character.
2. I have tested with lot many characters. file name with euro and pound are working fine.

Expected:
1. We should be allowing user to attach file with $ and % in their file name unless we are trying to avoid something critical.