When attempting to login to WordPress administration backend through /wp-admin/, you may encounter login failure issue with the following error message, despite the front-end (web pages) is working properly. You do not have sufficient permissions to access this page.
WordPress has built-in media uploader or file uploader which allows user to directly upload the files to the server via online inline interface without having to use a FTP or SFTP client, and subsequently allows user to manage the media and files. However, for security purpose, WordPress restricts the file types which you could upload using the built-in multi-file uploader or browser uploader.
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