Issue #2112247 by sihv, dgroene, aalamaki, Dennis Walgaard, mErilainen: Fixed Valid file extensions in file names are not properly enforced when uploading files.

Issue #2297947 by amitgoyal, andrewmacpherson: Clean up API docs for hook_file_mimetype_mapping_alter().

Issue #1914914 by purdy_nc, meba, chx, heyrocker: Add to docs of file_scan_directory to discuss excluding config

Issue #1921558 by ParisLiakos, xjm, Dave Reid: Convert file_get_mimetype() to use Symfony MimeTypeGuessers.

Issue #2003800 by jhedstrom, filijonka, YesCT, ParisLiakos, steeloctopus, damiankloip, sun, LinL, amateescu: Move drupal_check_memory_limit() and parse_size() functionality to components.

Issue #2221695 by brantwynn, ianthomas_uk, grom358, ParisLiakos, Jalandhar: Remove uses of deprecated URL functions.

Issue #1399846 by slashrsm, Gábor Hojtsy, Berdir, brantwynn, visabhishek, David_Rothstein, cweagans, martin107, SteffenR, Dave Reid: Make unused file 'cleanup' configurable.

Issue #2107287 by sun, amateescu: PHP 5.4 calls a new stream_metadata() method on stream wrappers not implemented by Drupal.

Issue #2140433 by pwolanin, chx, Owen Barton, dstol, Heine, Damien Tournoud: Port SA-CORE-2013-003 to Drupal 8.

Issue #2045927 by herom, martin107, ianthomas_uk, Xano, michaellander, Sutharsan: Replace all drupal_alter() deprecated function calls.

Issue #1165694 by pillarsdotnet, Sutharsan, droplet: Remove default nomask from file_scan_directory().

Issue #2121849 by moshe weitzman: Move chmod.directory and chmod.file out of config and into settings so that file writes are independant of the config system.

Temporary rollback since it conflicts with a critical issue.

This reverts commit ce08ea73.

Issue #2099205 by Wim Leers, zero2one, Gábor Hojtsy: When uploading and inserting an image trough the WYSIWYG plugin a relative path should be used for the image source (src) .

Issue #2084535 by mErilainen, tankerjoe, DanielFbrg: Fix file_copy documentation around the case when source and destination are the same

Issue #2099467 by moshe weitzman, chx: Let non-interactive installers determine mode of files directory and its subdirectories.

Issue #2089351 by thedavidmeister, meba: Convert all calls to check_plain() in core to Drupal\Component\Utility\String::checkPlain() in core/includes.

Issue #2100329 by cosmicdreams: Use \Drupal instead of Drupal to make IDEs and static code analyse tools happy.

Issue #1856766 by chx, Berdir, heyrocker, kim.pepper: Convert file_public_path() to the new settings system (make it not configurable via UI or YAML).

Issue #2045923 by drupalrv, tim.plunkett: Replace all module_invoke_all() deprecated function calls in procedural code.

Issue #1201024 by pillarsdotnet, jbrown, tim.plunket: drupal_realpath() should describe when it should be used.

Issue #2045189 by jlindsey15: Move file entity dependent code in includes/file.inc and system.module to file.module.

Issue #1987712 by dawehner, claudiu.cristea, damiankloip, andypost: Convert file_download() to a new style controller.