=== doc_core_api ===

[TYPO3-core] RFC: #16136: Change behaviour of check for allowed file extensions -> make it possible to really restrict to certain file extensions for filemounts

Chapter: Files: t3lib_extFileFunctions basics
Part: Web-space, FTP-space and $TYPO3_CONF_VARS['BE']['fileExtensions']

The control is done like this: if an extension matches 'deny' or 'deny' is set to '*', then the check returns FALSE. If the extension passes the 'deny' check and 'allow' is blank, set to '*' or the extension in the list of allowed extensions it returns TRUE.

To allow files without an extension, 'allow' must be set to '*'.