Allow ICO files upload

add_filter(

	'upload_mimes',

	function ( $mimes ) {

		// By default, only administrator users are allowed to add ICO files.

		// To enable more user types edit or comment the lines below but beware of

		// the security risks if you allow any user to upload ICO files.

		if ( ! current_user_can( 'administrator' ) ) {

			return $mimes;

		}

		$mimes['ico'] = 'image/x-icon';

		return $mimes;

	}

);

add_filter(

	'wp_check_filetype_and_ext',

	function ( $wp_check_filetype_and_ext, $file, $filename, $mimes, $real_mime ) {

		if ( ! $wp_check_filetype_and_ext['type'] ) {

			$check_filetype  = wp_check_filetype( $filename, $mimes );

			$ext             = $check_filetype['ext'];

			$type            = $check_filetype['type'];

			$proper_filename = $filename;

			if ( $type && 0 === strpos( $type, 'image/' ) && 'ico' !== $ext ) {

				$ext  = false;

				$type = false;

			}

			$wp_check_filetype_and_ext = compact( 'ext', 'type', 'proper_filename' );

		}

		return $wp_check_filetype_and_ext;

	},

	10,

	5

);