diff --git a/core/lib/Drupal/Component/Utility/Xss.php b/core/lib/Drupal/Component/Utility/Xss.php
index 423bde4..e31de8b 100644
--- a/core/lib/Drupal/Component/Utility/Xss.php
+++ b/core/lib/Drupal/Component/Utility/Xss.php
@@ -215,7 +215,7 @@ protected static function attributes($attributes) {
       switch ($mode) {
         case 0:
           // Attribute name, href for instance.
-          if (preg_match('/^([-a-zA-Z]+)/', $attributes, $match)) {
+          if (preg_match('/^([-a-zA-Z]+[-a-zA-Z0-9]*)/', $attributes, $match)) {
             $attribute_name = strtolower($match[1]);
             $skip = ($attribute_name == 'style' || substr($attribute_name, 0, 2) == 'on');
 
@@ -233,7 +233,7 @@ protected static function attributes($attributes) {
             ));
 
             $working = $mode = 1;
-            $attributes = preg_replace('/^[-a-zA-Z]+/', '', $attributes);
+            $attributes = preg_replace('/^[-a-zA-Z]+[-a-zA-Z0-9]*/', '', $attributes);
           }
           break;