The issue concerns stored XSS that can be triggered by remote authenticated administrators. This occurs when a file without an extension is uploaded, and in certain cases, this file is interpreted as text/html, allowing JavaScript content to be executed. The estimated number of potentially affected devices worldwide is not specified. Details about real-world incidents where this issue was exploited are not provided. The API endpoint "/admin/index.php?id=filesmanager" is involved, and the `id` variable is used to access the files manager. The lack of a file extension allows the file to be interpreted as text/html.