Asterisk(*) matched when it is contained within username on WAS 7

[amine spirit]

Hello,

I have a web application deployed on websphere 7 and use web authentication form (j_security_check).

The problem is that when the username used for authentication contains astersiks(*) it will be matched.

For example, a user that has the following credentials "username/password" can be authenticated by "user*/password" and this can be a security flaw.
I can also connect to the websphere 7 administration console with admin* while the username is administrator

I want to see if there is a special configuration on websphere 7 that disables asterisks matching on authencation.
Can anyone help me please?