Index: core/admin_templates/js/uploader/uploader.js
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- core/admin_templates/js/uploader/uploader.js	(revision 15713)
+++ core/admin_templates/js/uploader/uploader.js	(revision )
@@ -297,9 +297,27 @@
 
 Uploader.prototype.getFileIcon = function($filename) {
 	$filename.match(/\.([^.]*)$/);
-	var ext = RegExp.$1.toLowerCase();
+	var $ext = RegExp.$1.toLowerCase(),
+		$ext_overrides = {
+			'doc': '^(docx|dotx|docm|dotm)$',
+			'xls': '^(xlsx|xltx|xlsm|xltm|xlam|xlsb)$',
+			'ppt': '^(pptx|potx|ppsx|ppam|pptm|potm|ppsm)$'
+		};
 
-	$icon = ext.match(/^(ai|avi|bmp|cs|dll|doc|dot|exe|fla|gif|htm|html|jpg|js|mdb|mp3|pdf|ppt|rdp|swf|swt|txt|vsd|xls|xml|zip)$/) ? ext : 'default.icon';
+	$.each($ext_overrides, function ($new_ext, $expression) {
+		var $regexp = new RegExp($expression);
+
+		if ( $ext.match($regexp) ) {
+			$ext = $new_ext;
+
+			return false;
+		}
+
+		return true;
+	});
+
+	var $icon = $ext.match(/^(ai|avi|bmp|cs|dll|doc|dot|exe|fla|gif|htm|html|jpg|js|mdb|mp3|pdf|ppt|rdp|swf|swt|txt|vsd|xls|xml|zip)$/) ? $ext : 'default.icon';
+
 	return this.IconPath + '/' + $icon + '.gif';
 }
 
\ No newline at end of file
Index: core/kernel/globals.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- core/kernel/globals.php	(revision 15713)
+++ core/kernel/globals.php	(revision )
@@ -570,8 +570,13 @@
 	 */
 	public static function mimeContentType($file)
 	{
-		$ret = '';
+		$ret = self::vendorMimeContentType($file);
 
+		if ( $ret ) {
+			// vendor-specific mime types override any automatic detection
+			return $ret;
+		}
+
 		if ( function_exists('finfo_open') && function_exists('finfo_file') ) {
 			$mime_magic_resource = finfo_open(FILEINFO_MIME_TYPE);
 
@@ -585,7 +590,42 @@
 		}
 
 	    return $ret ? $ret : self::mimeContentTypeByExtension($file);
+ 	}
+
+	/**
+	 * Determines vendor-specific mime type from a given file
+	 *
+	 * @param string $file
+	 * @return bool
+	 * @access public
+	 * @static
+	 */
+	public static function vendorMimeContentType($file)
+	{
+		$file_extension = mb_strtolower( pathinfo($file, PATHINFO_EXTENSION) );
+
+		$mapping = Array (
+			'docx' => 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
+			'dotx' => 'application/vnd.openxmlformats-officedocument.wordprocessingml.template',
+			'docm' => 'application/vnd.ms-word.document.macroEnabled.12',
+			'dotm' => 'application/vnd.ms-word.template.macroEnabled.12',
+			'xlsx' => 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
+			'xltx' => 'application/vnd.openxmlformats-officedocument.spreadsheetml.template',
+			'xlsm' => 'application/vnd.ms-excel.sheet.macroEnabled.12',
+			'xltm' => 'application/vnd.ms-excel.template.macroEnabled.12',
+			'xlam' => 'application/vnd.ms-excel.addin.macroEnabled.12',
+			'xlsb' => 'application/vnd.ms-excel.sheet.binary.macroEnabled.12',
+			'pptx' => 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
+			'potx' => 'application/vnd.openxmlformats-officedocument.presentationml.template',
+			'ppsx' => 'application/vnd.openxmlformats-officedocument.presentationml.slideshow',
+			'ppam' => 'application/vnd.ms-powerpoint.addin.macroEnabled.12',
+			'pptm' => 'application/vnd.ms-powerpoint.presentation.macroEnabled.12',
+			'potm' => 'application/vnd.ms-powerpoint.template.macroEnabled.12',
+			'ppsm' => 'application/vnd.ms-powerpoint.slideshow.macroEnabled.12'
+		);
+
+		return isset($mapping[$file_extension]) ? $mapping[$file_extension] : false;
- 	}
+	}
 
 	/**
 	 * Detects mime type of the file purely based on it's extension
\ No newline at end of file