diff --git a/dist/cssfilter.js b/dist/cssfilter.js
index b2b430a..c17fa5b 100644
--- a/dist/cssfilter.js
+++ b/dist/cssfilter.js
@@ -27,9 +27,11 @@ function isNull (obj) {
  * @return {Object}
  */
 function shallowCopyObject (obj) {
-  var ret = {};
+  var ret = Object.create(null);
   for (var i in obj) {
-    ret[i] = obj[i];
+    if (obj.hasOwnProperty(i)) {
+      ret[i] = obj[i];
+    }
   }
   return ret;
 }
diff --git a/dist/cssfilter.min.js b/dist/cssfilter.min.js
index be53d4e..90389a7 100644
--- a/dist/cssfilter.min.js
+++ b/dist/cssfilter.min.js
@@ -1 +1 @@
-(function(){function r(e,n,t){function o(i,f){if(!n[i]){if(!e[i]){var c="function"==typeof require&&require;if(!f&&c)return c(i,!0);if(u)return u(i,!0);var a=new Error("Cannot find module '"+i+"'");throw a.code="MODULE_NOT_FOUND",a}var p=n[i]={exports:{}};e[i][0].call(p.exports,function(r){var n=e[i][1][r];return o(n||r)},p,p.exports,r,e,n,t)}return n[i].exports}for(var u="function"==typeof require&&require,i=0;i<t.length;i++)o(t[i]);return o}return r})()({1:[function(require,module,exports){var DEFAULT=require("./default");var parseStyle=require("./parser");var _=require("./util");function isNull(obj){return obj===undefined||obj===null}function shallowCopyObject(obj){var ret={};for(var i in obj){ret[i]=obj[i]}return ret}function FilterCSS(options){options=shallowCopyObject(options||{});options.whiteList=options.whiteList||DEFAULT.whiteList;options.onAttr=options.onAttr||DEFAULT.onAttr;options.onIgnoreAttr=options.onIgnoreAttr||DEFAULT.onIgnoreAttr;options.safeAttrValue=options.safeAttrValue||DEFAULT.safeAttrValue;this.options=options}FilterCSS.prototype.process=function(css){css=css||"";css=css.toString();if(!css)return"";var me=this;var options=me.options;var whiteList=options.whiteList;var onAttr=options.onAttr;var onIgnoreAttr=options.onIgnoreAttr;var safeAttrValue=options.safeAttrValue;var retCSS=parseStyle(css,function(sourcePosition,position,name,value,source){var check=whiteList[name];var isWhite=false;if(check===true)isWhite=check;else if(typeof check==="function")isWhite=check(value);else if(check instanceof RegExp)isWhite=check.test(value);if(isWhite!==true)isWhite=false;value=safeAttrValue(name,value);if(!value)return;var opts={position:position,sourcePosition:sourcePosition,source:source,isWhite:isWhite};if(isWhite){var ret=onAttr(name,value,opts);if(isNull(ret)){return name+":"+value}else{return ret}}else{var ret=onIgnoreAttr(name,value,opts);if(!isNull(ret)){return ret}}});return retCSS};module.exports=FilterCSS},{"./default":2,"./parser":4,"./util":5}],2:[function(require,module,exports){function getDefaultWhiteList(){var whiteList={};whiteList["align-content"]=false;whiteList["align-items"]=false;whiteList["align-self"]=false;whiteList["alignment-adjust"]=false;whiteList["alignment-baseline"]=false;whiteList["all"]=false;whiteList["anchor-point"]=false;whiteList["animation"]=false;whiteList["animation-delay"]=false;whiteList["animation-direction"]=false;whiteList["animation-duration"]=false;whiteList["animation-fill-mode"]=false;whiteList["animation-iteration-count"]=false;whiteList["animation-name"]=false;whiteList["animation-play-state"]=false;whiteList["animation-timing-function"]=false;whiteList["azimuth"]=false;whiteList["backface-visibility"]=false;whiteList["background"]=true;whiteList["background-attachment"]=true;whiteList["background-clip"]=true;whiteList["background-color"]=true;whiteList["background-image"]=true;whiteList["background-origin"]=true;whiteList["background-position"]=true;whiteList["background-repeat"]=true;whiteList["background-size"]=true;whiteList["baseline-shift"]=false;whiteList["binding"]=false;whiteList["bleed"]=false;whiteList["bookmark-label"]=false;whiteList["bookmark-level"]=false;whiteList["bookmark-state"]=false;whiteList["border"]=true;whiteList["border-bottom"]=true;whiteList["border-bottom-color"]=true;whiteList["border-bottom-left-radius"]=true;whiteList["border-bottom-right-radius"]=true;whiteList["border-bottom-style"]=true;whiteList["border-bottom-width"]=true;whiteList["border-collapse"]=true;whiteList["border-color"]=true;whiteList["border-image"]=true;whiteList["border-image-outset"]=true;whiteList["border-image-repeat"]=true;whiteList["border-image-slice"]=true;whiteList["border-image-source"]=true;whiteList["border-image-width"]=true;whiteList["border-left"]=true;whiteList["border-left-color"]=true;whiteList["border-left-style"]=true;whiteList["border-left-width"]=true;whiteList["border-radius"]=true;whiteList["border-right"]=true;whiteList["border-right-color"]=true;whiteList["border-right-style"]=true;whiteList["border-right-width"]=true;whiteList["border-spacing"]=true;whiteList["border-style"]=true;whiteList["border-top"]=true;whiteList["border-top-color"]=true;whiteList["border-top-left-radius"]=true;whiteList["border-top-right-radius"]=true;whiteList["border-top-style"]=true;whiteList["border-top-width"]=true;whiteList["border-width"]=true;whiteList["bottom"]=false;whiteList["box-decoration-break"]=true;whiteList["box-shadow"]=true;whiteList["box-sizing"]=true;whiteList["box-snap"]=true;whiteList["box-suppress"]=true;whiteList["break-after"]=true;whiteList["break-before"]=true;whiteList["break-inside"]=true;whiteList["caption-side"]=false;whiteList["chains"]=false;whiteList["clear"]=true;whiteList["clip"]=false;whiteList["clip-path"]=false;whiteList["clip-rule"]=false;whiteList["color"]=true;whiteList["color-interpolation-filters"]=true;whiteList["column-count"]=false;whiteList["column-fill"]=false;whiteList["column-gap"]=false;whiteList["column-rule"]=false;whiteList["column-rule-color"]=false;whiteList["column-rule-style"]=false;whiteList["column-rule-width"]=false;whiteList["column-span"]=false;whiteList["column-width"]=false;whiteList["columns"]=false;whiteList["contain"]=false;whiteList["content"]=false;whiteList["counter-increment"]=false;whiteList["counter-reset"]=false;whiteList["counter-set"]=false;whiteList["crop"]=false;whiteList["cue"]=false;whiteList["cue-after"]=false;whiteList["cue-before"]=false;whiteList["cursor"]=false;whiteList["direction"]=false;whiteList["display"]=true;whiteList["display-inside"]=true;whiteList["display-list"]=true;whiteList["display-outside"]=true;whiteList["dominant-baseline"]=false;whiteList["elevation"]=false;whiteList["empty-cells"]=false;whiteList["filter"]=false;whiteList["flex"]=false;whiteList["flex-basis"]=false;whiteList["flex-direction"]=false;whiteList["flex-flow"]=false;whiteList["flex-grow"]=false;whiteList["flex-shrink"]=false;whiteList["flex-wrap"]=false;whiteList["float"]=false;whiteList["float-offset"]=false;whiteList["flood-color"]=false;whiteList["flood-opacity"]=false;whiteList["flow-from"]=false;whiteList["flow-into"]=false;whiteList["font"]=true;whiteList["font-family"]=true;whiteList["font-feature-settings"]=true;whiteList["font-kerning"]=true;whiteList["font-language-override"]=true;whiteList["font-size"]=true;whiteList["font-size-adjust"]=true;whiteList["font-stretch"]=true;whiteList["font-style"]=true;whiteList["font-synthesis"]=true;whiteList["font-variant"]=true;whiteList["font-variant-alternates"]=true;whiteList["font-variant-caps"]=true;whiteList["font-variant-east-asian"]=true;whiteList["font-variant-ligatures"]=true;whiteList["font-variant-numeric"]=true;whiteList["font-variant-position"]=true;whiteList["font-weight"]=true;whiteList["gap"]=false;whiteList["grid"]=false;whiteList["grid-area"]=false;whiteList["grid-auto-columns"]=false;whiteList["grid-auto-flow"]=false;whiteList["grid-auto-rows"]=false;whiteList["grid-column"]=false;whiteList["grid-column-end"]=false;whiteList["grid-column-start"]=false;whiteList["grid-row"]=false;whiteList["grid-row-end"]=false;whiteList["grid-row-start"]=false;whiteList["grid-template"]=false;whiteList["grid-template-areas"]=false;whiteList["grid-template-columns"]=false;whiteList["grid-template-rows"]=false;whiteList["hanging-punctuation"]=false;whiteList["height"]=true;whiteList["hyphens"]=false;whiteList["icon"]=false;whiteList["image-orientation"]=false;whiteList["image-resolution"]=false;whiteList["ime-mode"]=false;whiteList["initial-letters"]=false;whiteList["inline-box-align"]=false;whiteList["justify-content"]=false;whiteList["justify-items"]=false;whiteList["justify-self"]=false;whiteList["left"]=false;whiteList["letter-spacing"]=true;whiteList["lighting-color"]=true;whiteList["line-box-contain"]=false;whiteList["line-break"]=false;whiteList["line-grid"]=false;whiteList["line-height"]=false;whiteList["line-snap"]=false;whiteList["line-stacking"]=false;whiteList["line-stacking-ruby"]=false;whiteList["line-stacking-shift"]=false;whiteList["line-stacking-strategy"]=false;whiteList["list-style"]=true;whiteList["list-style-image"]=true;whiteList["list-style-position"]=true;whiteList["list-style-type"]=true;whiteList["margin"]=true;whiteList["margin-bottom"]=true;whiteList["margin-left"]=true;whiteList["margin-right"]=true;whiteList["margin-top"]=true;whiteList["marker-offset"]=false;whiteList["marker-side"]=false;whiteList["marks"]=false;whiteList["mask"]=false;whiteList["mask-box"]=false;whiteList["mask-box-outset"]=false;whiteList["mask-box-repeat"]=false;whiteList["mask-box-slice"]=false;whiteList["mask-box-source"]=false;whiteList["mask-box-width"]=false;whiteList["mask-clip"]=false;whiteList["mask-image"]=false;whiteList["mask-origin"]=false;whiteList["mask-position"]=false;whiteList["mask-repeat"]=false;whiteList["mask-size"]=false;whiteList["mask-source-type"]=false;whiteList["mask-type"]=false;whiteList["max-height"]=true;whiteList["max-lines"]=false;whiteList["max-width"]=true;whiteList["min-height"]=true;whiteList["min-width"]=true;whiteList["move-to"]=false;whiteList["nav-down"]=false;whiteList["nav-index"]=false;whiteList["nav-left"]=false;whiteList["nav-right"]=false;whiteList["nav-up"]=false;whiteList["object-fit"]=false;whiteList["object-position"]=false;whiteList["opacity"]=false;whiteList["order"]=false;whiteList["orphans"]=false;whiteList["outline"]=false;whiteList["outline-color"]=false;whiteList["outline-offset"]=false;whiteList["outline-style"]=false;whiteList["outline-width"]=false;whiteList["overflow"]=false;whiteList["overflow-wrap"]=false;whiteList["overflow-x"]=false;whiteList["overflow-y"]=false;whiteList["padding"]=true;whiteList["padding-bottom"]=true;whiteList["padding-left"]=true;whiteList["padding-right"]=true;whiteList["padding-top"]=true;whiteList["page"]=false;whiteList["page-break-after"]=false;whiteList["page-break-before"]=false;whiteList["page-break-inside"]=false;whiteList["page-policy"]=false;whiteList["pause"]=false;whiteList["pause-after"]=false;whiteList["pause-before"]=false;whiteList["perspective"]=false;whiteList["perspective-origin"]=false;whiteList["pitch"]=false;whiteList["pitch-range"]=false;whiteList["play-during"]=false;whiteList["position"]=false;whiteList["presentation-level"]=false;whiteList["quotes"]=false;whiteList["region-fragment"]=false;whiteList["resize"]=false;whiteList["rest"]=false;whiteList["rest-after"]=false;whiteList["rest-before"]=false;whiteList["richness"]=false;whiteList["right"]=false;whiteList["rotation"]=false;whiteList["rotation-point"]=false;whiteList["row-gap"]=false;whiteList["ruby-align"]=false;whiteList["ruby-merge"]=false;whiteList["ruby-position"]=false;whiteList["shape-image-threshold"]=false;whiteList["shape-outside"]=false;whiteList["shape-margin"]=false;whiteList["size"]=false;whiteList["speak"]=false;whiteList["speak-as"]=false;whiteList["speak-header"]=false;whiteList["speak-numeral"]=false;whiteList["speak-punctuation"]=false;whiteList["speech-rate"]=false;whiteList["stress"]=false;whiteList["string-set"]=false;whiteList["tab-size"]=false;whiteList["table-layout"]=false;whiteList["text-align"]=true;whiteList["text-align-last"]=true;whiteList["text-combine-upright"]=true;whiteList["text-decoration"]=true;whiteList["text-decoration-color"]=true;whiteList["text-decoration-line"]=true;whiteList["text-decoration-skip"]=true;whiteList["text-decoration-style"]=true;whiteList["text-emphasis"]=true;whiteList["text-emphasis-color"]=true;whiteList["text-emphasis-position"]=true;whiteList["text-emphasis-style"]=true;whiteList["text-height"]=true;whiteList["text-indent"]=true;whiteList["text-justify"]=true;whiteList["text-orientation"]=true;whiteList["text-overflow"]=true;whiteList["text-shadow"]=true;whiteList["text-space-collapse"]=true;whiteList["text-transform"]=true;whiteList["text-underline-position"]=true;whiteList["text-wrap"]=true;whiteList["top"]=false;whiteList["transform"]=false;whiteList["transform-origin"]=false;whiteList["transform-style"]=false;whiteList["transition"]=false;whiteList["transition-delay"]=false;whiteList["transition-duration"]=false;whiteList["transition-property"]=false;whiteList["transition-timing-function"]=false;whiteList["unicode-bidi"]=false;whiteList["vertical-align"]=false;whiteList["visibility"]=false;whiteList["voice-balance"]=false;whiteList["voice-duration"]=false;whiteList["voice-family"]=false;whiteList["voice-pitch"]=false;whiteList["voice-range"]=false;whiteList["voice-rate"]=false;whiteList["voice-stress"]=false;whiteList["voice-volume"]=false;whiteList["volume"]=false;whiteList["white-space"]=false;whiteList["widows"]=false;whiteList["width"]=true;whiteList["will-change"]=false;whiteList["word-break"]=true;whiteList["word-spacing"]=true;whiteList["word-wrap"]=true;whiteList["wrap-flow"]=false;whiteList["wrap-through"]=false;whiteList["writing-mode"]=false;whiteList["z-index"]=false;return whiteList}function onAttr(name,value,options){}function onIgnoreAttr(name,value,options){}var REGEXP_URL_JAVASCRIPT=/javascript\s*\:/gim;function safeAttrValue(name,value){if(REGEXP_URL_JAVASCRIPT.test(value))return"";return value}exports.whiteList=getDefaultWhiteList();exports.getDefaultWhiteList=getDefaultWhiteList;exports.onAttr=onAttr;exports.onIgnoreAttr=onIgnoreAttr;exports.safeAttrValue=safeAttrValue},{}],3:[function(require,module,exports){var DEFAULT=require("./default");var FilterCSS=require("./css");function filterCSS(html,options){var xss=new FilterCSS(options);return xss.process(html)}exports=module.exports=filterCSS;exports.FilterCSS=FilterCSS;for(var i in DEFAULT)exports[i]=DEFAULT[i];if(typeof window!=="undefined"){window.filterCSS=module.exports}},{"./css":1,"./default":2}],4:[function(require,module,exports){var _=require("./util");function parseStyle(css,onAttr){css=_.trimRight(css);if(css[css.length-1]!==";")css+=";";var cssLength=css.length;var isParenthesisOpen=false;var lastPos=0;var i=0;var retCSS="";function addNewAttr(){if(!isParenthesisOpen){var source=_.trim(css.slice(lastPos,i));var j=source.indexOf(":");if(j!==-1){var name=_.trim(source.slice(0,j));var value=_.trim(source.slice(j+1));if(name){var ret=onAttr(lastPos,retCSS.length,name,value,source);if(ret)retCSS+=ret+"; "}}}lastPos=i+1}for(;i<cssLength;i++){var c=css[i];if(c==="/"&&css[i+1]==="*"){var j=css.indexOf("*/",i+2);if(j===-1)break;i=j+1;lastPos=i+1;isParenthesisOpen=false}else if(c==="("){isParenthesisOpen=true}else if(c===")"){isParenthesisOpen=false}else if(c===";"){if(isParenthesisOpen){}else{addNewAttr()}}else if(c==="\n"){addNewAttr()}}return _.trim(retCSS)}module.exports=parseStyle},{"./util":5}],5:[function(require,module,exports){module.exports={indexOf:function(arr,item){var i,j;if(Array.prototype.indexOf){return arr.indexOf(item)}for(i=0,j=arr.length;i<j;i++){if(arr[i]===item){return i}}return-1},forEach:function(arr,fn,scope){var i,j;if(Array.prototype.forEach){return arr.forEach(fn,scope)}for(i=0,j=arr.length;i<j;i++){fn.call(scope,arr[i],i,arr)}},trim:function(str){if(String.prototype.trim){return str.trim()}return str.replace(/(^\s*)|(\s*$)/g,"")},trimRight:function(str){if(String.prototype.trimRight){return str.trimRight()}return str.replace(/(\s*$)/g,"")}}},{}]},{},[3]);
\ No newline at end of file
+(function(){function r(e,n,t){function o(i,f){if(!n[i]){if(!e[i]){var c="function"==typeof require&&require;if(!f&&c)return c(i,!0);if(u)return u(i,!0);var a=new Error("Cannot find module '"+i+"'");throw a.code="MODULE_NOT_FOUND",a}var p=n[i]={exports:{}};e[i][0].call(p.exports,function(r){var n=e[i][1][r];return o(n||r)},p,p.exports,r,e,n,t)}return n[i].exports}for(var u="function"==typeof require&&require,i=0;i<t.length;i++)o(t[i]);return o}return r})()({1:[function(require,module,exports){var DEFAULT=require("./default");var parseStyle=require("./parser");var _=require("./util");function isNull(obj){return obj===undefined||obj===null}function shallowCopyObject(obj){var ret=Object.create(null);for(var i in obj){if(obj.hasOwnProperty(i)){ret[i]=obj[i]}}return ret}function FilterCSS(options){options=shallowCopyObject(options||{});options.whiteList=options.whiteList||DEFAULT.whiteList;options.onAttr=options.onAttr||DEFAULT.onAttr;options.onIgnoreAttr=options.onIgnoreAttr||DEFAULT.onIgnoreAttr;options.safeAttrValue=options.safeAttrValue||DEFAULT.safeAttrValue;this.options=options}FilterCSS.prototype.process=function(css){css=css||"";css=css.toString();if(!css)return"";var me=this;var options=me.options;var whiteList=options.whiteList;var onAttr=options.onAttr;var onIgnoreAttr=options.onIgnoreAttr;var safeAttrValue=options.safeAttrValue;var retCSS=parseStyle(css,function(sourcePosition,position,name,value,source){var check=whiteList[name];var isWhite=false;if(check===true)isWhite=check;else if(typeof check==="function")isWhite=check(value);else if(check instanceof RegExp)isWhite=check.test(value);if(isWhite!==true)isWhite=false;value=safeAttrValue(name,value);if(!value)return;var opts={position:position,sourcePosition:sourcePosition,source:source,isWhite:isWhite};if(isWhite){var ret=onAttr(name,value,opts);if(isNull(ret)){return name+":"+value}else{return ret}}else{var ret=onIgnoreAttr(name,value,opts);if(!isNull(ret)){return ret}}});return retCSS};module.exports=FilterCSS},{"./default":2,"./parser":4,"./util":5}],2:[function(require,module,exports){function getDefaultWhiteList(){var whiteList={};whiteList["align-content"]=false;whiteList["align-items"]=false;whiteList["align-self"]=false;whiteList["alignment-adjust"]=false;whiteList["alignment-baseline"]=false;whiteList["all"]=false;whiteList["anchor-point"]=false;whiteList["animation"]=false;whiteList["animation-delay"]=false;whiteList["animation-direction"]=false;whiteList["animation-duration"]=false;whiteList["animation-fill-mode"]=false;whiteList["animation-iteration-count"]=false;whiteList["animation-name"]=false;whiteList["animation-play-state"]=false;whiteList["animation-timing-function"]=false;whiteList["azimuth"]=false;whiteList["backface-visibility"]=false;whiteList["background"]=true;whiteList["background-attachment"]=true;whiteList["background-clip"]=true;whiteList["background-color"]=true;whiteList["background-image"]=true;whiteList["background-origin"]=true;whiteList["background-position"]=true;whiteList["background-repeat"]=true;whiteList["background-size"]=true;whiteList["baseline-shift"]=false;whiteList["binding"]=false;whiteList["bleed"]=false;whiteList["bookmark-label"]=false;whiteList["bookmark-level"]=false;whiteList["bookmark-state"]=false;whiteList["border"]=true;whiteList["border-bottom"]=true;whiteList["border-bottom-color"]=true;whiteList["border-bottom-left-radius"]=true;whiteList["border-bottom-right-radius"]=true;whiteList["border-bottom-style"]=true;whiteList["border-bottom-width"]=true;whiteList["border-collapse"]=true;whiteList["border-color"]=true;whiteList["border-image"]=true;whiteList["border-image-outset"]=true;whiteList["border-image-repeat"]=true;whiteList["border-image-slice"]=true;whiteList["border-image-source"]=true;whiteList["border-image-width"]=true;whiteList["border-left"]=true;whiteList["border-left-color"]=true;whiteList["border-left-style"]=true;whiteList["border-left-width"]=true;whiteList["border-radius"]=true;whiteList["border-right"]=true;whiteList["border-right-color"]=true;whiteList["border-right-style"]=true;whiteList["border-right-width"]=true;whiteList["border-spacing"]=true;whiteList["border-style"]=true;whiteList["border-top"]=true;whiteList["border-top-color"]=true;whiteList["border-top-left-radius"]=true;whiteList["border-top-right-radius"]=true;whiteList["border-top-style"]=true;whiteList["border-top-width"]=true;whiteList["border-width"]=true;whiteList["bottom"]=false;whiteList["box-decoration-break"]=true;whiteList["box-shadow"]=true;whiteList["box-sizing"]=true;whiteList["box-snap"]=true;whiteList["box-suppress"]=true;whiteList["break-after"]=true;whiteList["break-before"]=true;whiteList["break-inside"]=true;whiteList["caption-side"]=false;whiteList["chains"]=false;whiteList["clear"]=true;whiteList["clip"]=false;whiteList["clip-path"]=false;whiteList["clip-rule"]=false;whiteList["color"]=true;whiteList["color-interpolation-filters"]=true;whiteList["column-count"]=false;whiteList["column-fill"]=false;whiteList["column-gap"]=false;whiteList["column-rule"]=false;whiteList["column-rule-color"]=false;whiteList["column-rule-style"]=false;whiteList["column-rule-width"]=false;whiteList["column-span"]=false;whiteList["column-width"]=false;whiteList["columns"]=false;whiteList["contain"]=false;whiteList["content"]=false;whiteList["counter-increment"]=false;whiteList["counter-reset"]=false;whiteList["counter-set"]=false;whiteList["crop"]=false;whiteList["cue"]=false;whiteList["cue-after"]=false;whiteList["cue-before"]=false;whiteList["cursor"]=false;whiteList["direction"]=false;whiteList["display"]=true;whiteList["display-inside"]=true;whiteList["display-list"]=true;whiteList["display-outside"]=true;whiteList["dominant-baseline"]=false;whiteList["elevation"]=false;whiteList["empty-cells"]=false;whiteList["filter"]=false;whiteList["flex"]=false;whiteList["flex-basis"]=false;whiteList["flex-direction"]=false;whiteList["flex-flow"]=false;whiteList["flex-grow"]=false;whiteList["flex-shrink"]=false;whiteList["flex-wrap"]=false;whiteList["float"]=false;whiteList["float-offset"]=false;whiteList["flood-color"]=false;whiteList["flood-opacity"]=false;whiteList["flow-from"]=false;whiteList["flow-into"]=false;whiteList["font"]=true;whiteList["font-family"]=true;whiteList["font-feature-settings"]=true;whiteList["font-kerning"]=true;whiteList["font-language-override"]=true;whiteList["font-size"]=true;whiteList["font-size-adjust"]=true;whiteList["font-stretch"]=true;whiteList["font-style"]=true;whiteList["font-synthesis"]=true;whiteList["font-variant"]=true;whiteList["font-variant-alternates"]=true;whiteList["font-variant-caps"]=true;whiteList["font-variant-east-asian"]=true;whiteList["font-variant-ligatures"]=true;whiteList["font-variant-numeric"]=true;whiteList["font-variant-position"]=true;whiteList["font-weight"]=true;whiteList["gap"]=false;whiteList["grid"]=false;whiteList["grid-area"]=false;whiteList["grid-auto-columns"]=false;whiteList["grid-auto-flow"]=false;whiteList["grid-auto-rows"]=false;whiteList["grid-column"]=false;whiteList["grid-column-end"]=false;whiteList["grid-column-start"]=false;whiteList["grid-row"]=false;whiteList["grid-row-end"]=false;whiteList["grid-row-start"]=false;whiteList["grid-template"]=false;whiteList["grid-template-areas"]=false;whiteList["grid-template-columns"]=false;whiteList["grid-template-rows"]=false;whiteList["hanging-punctuation"]=false;whiteList["height"]=true;whiteList["hyphens"]=false;whiteList["icon"]=false;whiteList["image-orientation"]=false;whiteList["image-resolution"]=false;whiteList["ime-mode"]=false;whiteList["initial-letters"]=false;whiteList["inline-box-align"]=false;whiteList["justify-content"]=false;whiteList["justify-items"]=false;whiteList["justify-self"]=false;whiteList["left"]=false;whiteList["letter-spacing"]=true;whiteList["lighting-color"]=true;whiteList["line-box-contain"]=false;whiteList["line-break"]=false;whiteList["line-grid"]=false;whiteList["line-height"]=false;whiteList["line-snap"]=false;whiteList["line-stacking"]=false;whiteList["line-stacking-ruby"]=false;whiteList["line-stacking-shift"]=false;whiteList["line-stacking-strategy"]=false;whiteList["list-style"]=true;whiteList["list-style-image"]=true;whiteList["list-style-position"]=true;whiteList["list-style-type"]=true;whiteList["margin"]=true;whiteList["margin-bottom"]=true;whiteList["margin-left"]=true;whiteList["margin-right"]=true;whiteList["margin-top"]=true;whiteList["marker-offset"]=false;whiteList["marker-side"]=false;whiteList["marks"]=false;whiteList["mask"]=false;whiteList["mask-box"]=false;whiteList["mask-box-outset"]=false;whiteList["mask-box-repeat"]=false;whiteList["mask-box-slice"]=false;whiteList["mask-box-source"]=false;whiteList["mask-box-width"]=false;whiteList["mask-clip"]=false;whiteList["mask-image"]=false;whiteList["mask-origin"]=false;whiteList["mask-position"]=false;whiteList["mask-repeat"]=false;whiteList["mask-size"]=false;whiteList["mask-source-type"]=false;whiteList["mask-type"]=false;whiteList["max-height"]=true;whiteList["max-lines"]=false;whiteList["max-width"]=true;whiteList["min-height"]=true;whiteList["min-width"]=true;whiteList["move-to"]=false;whiteList["nav-down"]=false;whiteList["nav-index"]=false;whiteList["nav-left"]=false;whiteList["nav-right"]=false;whiteList["nav-up"]=false;whiteList["object-fit"]=false;whiteList["object-position"]=false;whiteList["opacity"]=false;whiteList["order"]=false;whiteList["orphans"]=false;whiteList["outline"]=false;whiteList["outline-color"]=false;whiteList["outline-offset"]=false;whiteList["outline-style"]=false;whiteList["outline-width"]=false;whiteList["overflow"]=false;whiteList["overflow-wrap"]=false;whiteList["overflow-x"]=false;whiteList["overflow-y"]=false;whiteList["padding"]=true;whiteList["padding-bottom"]=true;whiteList["padding-left"]=true;whiteList["padding-right"]=true;whiteList["padding-top"]=true;whiteList["page"]=false;whiteList["page-break-after"]=false;whiteList["page-break-before"]=false;whiteList["page-break-inside"]=false;whiteList["page-policy"]=false;whiteList["pause"]=false;whiteList["pause-after"]=false;whiteList["pause-before"]=false;whiteList["perspective"]=false;whiteList["perspective-origin"]=false;whiteList["pitch"]=false;whiteList["pitch-range"]=false;whiteList["play-during"]=false;whiteList["position"]=false;whiteList["presentation-level"]=false;whiteList["quotes"]=false;whiteList["region-fragment"]=false;whiteList["resize"]=false;whiteList["rest"]=false;whiteList["rest-after"]=false;whiteList["rest-before"]=false;whiteList["richness"]=false;whiteList["right"]=false;whiteList["rotation"]=false;whiteList["rotation-point"]=false;whiteList["row-gap"]=false;whiteList["ruby-align"]=false;whiteList["ruby-merge"]=false;whiteList["ruby-position"]=false;whiteList["shape-image-threshold"]=false;whiteList["shape-outside"]=false;whiteList["shape-margin"]=false;whiteList["size"]=false;whiteList["speak"]=false;whiteList["speak-as"]=false;whiteList["speak-header"]=false;whiteList["speak-numeral"]=false;whiteList["speak-punctuation"]=false;whiteList["speech-rate"]=false;whiteList["stress"]=false;whiteList["string-set"]=false;whiteList["tab-size"]=false;whiteList["table-layout"]=false;whiteList["text-align"]=true;whiteList["text-align-last"]=true;whiteList["text-combine-upright"]=true;whiteList["text-decoration"]=true;whiteList["text-decoration-color"]=true;whiteList["text-decoration-line"]=true;whiteList["text-decoration-skip"]=true;whiteList["text-decoration-style"]=true;whiteList["text-emphasis"]=true;whiteList["text-emphasis-color"]=true;whiteList["text-emphasis-position"]=true;whiteList["text-emphasis-style"]=true;whiteList["text-height"]=true;whiteList["text-indent"]=true;whiteList["text-justify"]=true;whiteList["text-orientation"]=true;whiteList["text-overflow"]=true;whiteList["text-shadow"]=true;whiteList["text-space-collapse"]=true;whiteList["text-transform"]=true;whiteList["text-underline-position"]=true;whiteList["text-wrap"]=true;whiteList["top"]=false;whiteList["transform"]=false;whiteList["transform-origin"]=false;whiteList["transform-style"]=false;whiteList["transition"]=false;whiteList["transition-delay"]=false;whiteList["transition-duration"]=false;whiteList["transition-property"]=false;whiteList["transition-timing-function"]=false;whiteList["unicode-bidi"]=false;whiteList["vertical-align"]=false;whiteList["visibility"]=false;whiteList["voice-balance"]=false;whiteList["voice-duration"]=false;whiteList["voice-family"]=false;whiteList["voice-pitch"]=false;whiteList["voice-range"]=false;whiteList["voice-rate"]=false;whiteList["voice-stress"]=false;whiteList["voice-volume"]=false;whiteList["volume"]=false;whiteList["white-space"]=false;whiteList["widows"]=false;whiteList["width"]=true;whiteList["will-change"]=false;whiteList["word-break"]=true;whiteList["word-spacing"]=true;whiteList["word-wrap"]=true;whiteList["wrap-flow"]=false;whiteList["wrap-through"]=false;whiteList["writing-mode"]=false;whiteList["z-index"]=false;return whiteList}function onAttr(name,value,options){}function onIgnoreAttr(name,value,options){}var REGEXP_URL_JAVASCRIPT=/javascript\s*\:/gim;function safeAttrValue(name,value){if(REGEXP_URL_JAVASCRIPT.test(value))return"";return value}exports.whiteList=getDefaultWhiteList();exports.getDefaultWhiteList=getDefaultWhiteList;exports.onAttr=onAttr;exports.onIgnoreAttr=onIgnoreAttr;exports.safeAttrValue=safeAttrValue},{}],3:[function(require,module,exports){var DEFAULT=require("./default");var FilterCSS=require("./css");function filterCSS(html,options){var xss=new FilterCSS(options);return xss.process(html)}exports=module.exports=filterCSS;exports.FilterCSS=FilterCSS;for(var i in DEFAULT)exports[i]=DEFAULT[i];if(typeof window!=="undefined"){window.filterCSS=module.exports}},{"./css":1,"./default":2}],4:[function(require,module,exports){var _=require("./util");function parseStyle(css,onAttr){css=_.trimRight(css);if(css[css.length-1]!==";")css+=";";var cssLength=css.length;var isParenthesisOpen=false;var lastPos=0;var i=0;var retCSS="";function addNewAttr(){if(!isParenthesisOpen){var source=_.trim(css.slice(lastPos,i));var j=source.indexOf(":");if(j!==-1){var name=_.trim(source.slice(0,j));var value=_.trim(source.slice(j+1));if(name){var ret=onAttr(lastPos,retCSS.length,name,value,source);if(ret)retCSS+=ret+"; "}}}lastPos=i+1}for(;i<cssLength;i++){var c=css[i];if(c==="/"&&css[i+1]==="*"){var j=css.indexOf("*/",i+2);if(j===-1)break;i=j+1;lastPos=i+1;isParenthesisOpen=false}else if(c==="("){isParenthesisOpen=true}else if(c===")"){isParenthesisOpen=false}else if(c===";"){if(isParenthesisOpen){}else{addNewAttr()}}else if(c==="\n"){addNewAttr()}}return _.trim(retCSS)}module.exports=parseStyle},{"./util":5}],5:[function(require,module,exports){module.exports={indexOf:function(arr,item){var i,j;if(Array.prototype.indexOf){return arr.indexOf(item)}for(i=0,j=arr.length;i<j;i++){if(arr[i]===item){return i}}return-1},forEach:function(arr,fn,scope){var i,j;if(Array.prototype.forEach){return arr.forEach(fn,scope)}for(i=0,j=arr.length;i<j;i++){fn.call(scope,arr[i],i,arr)}},trim:function(str){if(String.prototype.trim){return str.trim()}return str.replace(/(^\s*)|(\s*$)/g,"")},trimRight:function(str){if(String.prototype.trimRight){return str.trimRight()}return str.replace(/(\s*$)/g,"")}}},{}]},{},[3]);
\ No newline at end of file
diff --git a/lib/css.js b/lib/css.js
index 49e9707..d4c09c8 100644
--- a/lib/css.js
+++ b/lib/css.js
@@ -26,9 +26,11 @@ function isNull (obj) {
  * @return {Object}
  */
 function shallowCopyObject (obj) {
-  var ret = {};
+  var ret = Object.create(null);
   for (var i in obj) {
-    ret[i] = obj[i];
+    if (obj.hasOwnProperty(i)) {
+      ret[i] = obj[i];
+    }
   }
   return ret;
 }