HTTP Basic Authentication on WebLogic starting from version 9.2 (previous versions were not tested) works not correctly. The problem is that if there is some request to your application with "Authorization" header the request will be intercepted by WebLogic itself and will not be passed to your application. WebLogic will try to make authentication itself.
Such problem can occur in your application if you are using HTTP Basic Authentication with Acegi/Spring Security.
The only solution I have found to resolve the issue is to add
into the config.xml file (before closing tag
This configuration will resolve the issue.