DNN (formerly DotNetNuke) is an open-source web content management platform (CMS) in the Microsoft ecosystem. Prior to version 10.1.0, the CKEditor file upload endpoint has insufficient sanitization for filenames allowing probing network endpoints. A specially crafted request can be made to upload a file with Unicode characters, which would be translated into a path that could expose resources in the internal network of the hosted site. This issue has been patched in version 10.1.0.