All users are displayed for '%' and '_' in search result in 'User Groups' window

When you enter some symbol or their combinations in the text-field 'Filter' in 'User Groups' page, pop-up window with mismatching user names appears. But when you add in this field '%' or '_' symbol, all users are shown in pop-up.

Precondition: user group with name contains % and _ should be created

Steps:
1. Login in Admin Panel and go to Users->User Groups window.
2. Add '%' in text field and Click Search

Actual Result: All user names appears in the pop-up window (see screenshot "GrSearch2" attached)
Expected Result: Only user name, containing '%' should appear

3. Add '_' in text field and Click Search

Actual Result: All user names appears in the pop-up window (see screenshot "GrSearch1" attached)
Expected Result: Only user name, containing '_' should appear