If you feel there is a bug in CKFinder, go to the community forum and report your findings. Before you do this, however, try to reproduce the error on the CKFinder demo site. If you are using an older version of the software and the demo (always running the latest release) works correctly, you should try to upgrade first as it is possible that the issue might already be fixed.
Please make sure that you provide all the information that can make it easier for the developers to examine the issue. It is necessary to describe the environment where the error occurs in as much detail as possible (CKFinder version, server side language, server name and version, browser, your CKFinder configuration) and provide steps to reproduce it. If any error messages are returned, please include them, too.
A good idea is to provide a screenshot showing the issue — this is particularly useful in all cases related to the application interface. If a problem occurs during the upload of a particular file, either attach it or give the file name and describe its type and size.