Fix #155

src/HtmlSanitizer/HtmlSanitizer.cs

@@ -538,6 +538,7 @@ namespace Ganss.XSS
                 }
 
                 // sanitize the style attribute
+                var oldStyleEmpty = string.IsNullOrEmpty(tag.GetAttribute("style"));
                 SanitizeStyle(tag, baseUrl);
 
                 var checkClasses = AllowedCssClasses != null;
@@ -564,9 +565,9 @@ namespace Ganss.XSS
                             if (!tag.ClassList.Any())
                                 RemoveAttribute(tag, attribute, RemoveReason.ClassAttributeEmpty);
                         }
-                        else if (string.IsNullOrEmpty(attribute.Value))
+                        else if (!oldStyleEmpty && attribute.Name == "style" && string.IsNullOrEmpty(attribute.Value))
                         {
-                            tag.RemoveAttribute(attribute.Name);
+                            RemoveAttribute(tag, attribute, RemoveReason.StyleAttributeEmpty);
                         }
                     }
                 }

src/HtmlSanitizer/RemoveReason.cs

@@ -32,6 +32,10 @@
         /// <summary>
         /// The class attribute is empty
         /// </summary>
-        ClassAttributeEmpty
+        ClassAttributeEmpty,
+        /// <summary>
+        /// The style attribute is empty
+        /// </summary>
+        StyleAttributeEmpty,
     }
 }