Incorrect Access Control in the FileEditor (/Admin/Views/FileEditor/) in FlexDotnetCMS before v1.5.11 allows an authenticated remote attacker to read and write to existing files outside the web root. The files can be accessed via directory traversal, i.e., by entering a .. (dot dot) path such as ..\..\..\..\..\<file> in the input field of the FileEditor. In FlexDotnetCMS before v1.5.8, it is also possible to access files by specifying the full path (e.g., C:\<file>). The files can then be edited via the FileEditor.