There is a trivial bug in the enduser UI when changing a security answer.
Steps to reproduce:
1) Log in to the admin console, create a security question and then a new user.
2) Log out and log into the enduser console as that user.
3) Select the security question and give an answer, save the changes.
4) Log back into enduser as that user. The security answer textfield is greyed out.
You can "ungrey" the textfield by changing the security question to "Select Security Question", writing some text in the textfield, and then selecting the actual security question again.