diff --git a/source b/source
index 4f422ad497a..fcb55a4b74c 100644
--- a/source
+++ b/source
@@ -57856,6 +57856,12 @@ o............A....e
   <span data-x="prepare a script">prepared</span>, based on the <code
   data-x="attr-script-src">src</code> attribute of the element at that time.</p>
 
+  <p>The seventh is a flag indicating whether or not the script has a <dfn
+  data-x="concept-script-duplicate-attribute">duplicate attribute</dfn>. This flag is intially
+  unset and can be set after the tokenizer <span data-x="create an element for the token">creates
+  the element</span>. This flag is used for security checks in <cite>Content Security
+  Policy</cite>. <ref spec="CSP"></p>
+
   <p>Finally, a <code>script</code> element has <dfn data-x="concept-script-script"
   data-export="">the script's script</dfn>, which is a <span data-x="concept-script">script</span>
   resulting from <span data-x="prepare a script">preparing</span> the element. This is set
@@ -103059,12 +103065,14 @@ dictionary <dfn>StorageEventInit</dfn> : <span>EventInit</span> {
   DOCTYPE, start tag, end tag, comment, character, end-of-file. DOCTYPE tokens have a name, a public
   identifier, a system identifier, and a <dfn><i>force-quirks flag</i></dfn>. When a DOCTYPE token
   is created, its name, public identifier, and system identifier must be marked as missing (which is
-  a distinct state from the empty string), and the <i data-x="force-quirks flag">force-quirks flag</i> must be set to
-  <i>off</i> (its other state is <i>on</i>). Start and end tag tokens have a tag name, a <dfn
-  data-x="self-closing flag">self-closing flag</dfn>, and a list of attributes, each of which has a
-  name and a value. When a start or end tag token is created, its <i data-x="self-closing
-  flag">self-closing flag</i> must be unset (its other state is that it be set), and its attributes
-  list must be empty. Comment and character tokens have data.</p>
+  a distinct state from the empty string), and the <i data-x="force-quirks flag">force-quirks flag</i>
+  must be set to <i>off</i> (its other state is <i>on</i>). Start and end tag tokens have a tag name,
+  a <dfn data-x="self-closing flag">self-closing flag</dfn>, a <dfn data-x="duplicate attribute
+  flag">duplicate attribute flag</dfn>, and a list of attributes, each of which has a name and a
+  value. When a start or end tag token is created, its <i data-x="self-closing flag">self-closing
+  flag</i> must be unset (its other state is that it be set), its <i data-x="duplicate attribute
+  flag"> duplicate attribute flag</i> must be unset (its other state is that it be set), and its
+  attributes list must be empty. Comment and character tokens have data.</p>
 
   <p>When a token is emitted, it must immediately be handled by the <span>tree construction</span>
   stage. The tree construction stage can affect the state of the tokenization stage, and can insert
@@ -104054,8 +104062,9 @@ dictionary <dfn>StorageEventInit</dfn> : <span>EventInit</span> {
   <p>When the user agent leaves the attribute name state (and before emitting the tag token, if
   appropriate), the complete attribute's name must be compared to the other attributes on the same
   token; if there is already an attribute on the token with the exact same name, then this is a
-  <span data-x="parse-error-duplicate-attribute">duplicate-attribute</span> <span>parse error</span>
-  and the new attribute must be removed from the token.</p>
+  <span data-x="parse-error-duplicate-attribute">duplicate-attribute</span> <span>parse error</span>,
+  the new attribute must be removed from the token, and the token's <i data-x="duplicate attribute
+  flag">duplicate attribute flag</i> must be set.</p>
 
   <p class="note">If an attribute is so removed from a token, it, and the value that gets associated
   with it, if any, are never subsequently used by the parser, and are therefore effectively
@@ -105747,6 +105756,13 @@ dictionary <dfn>StorageEventInit</dfn> : <span>EventInit</span> {
     data-x="dom-document-open">the document to be blown away</span>.</p>
    </li>
 
+   <li>
+    <p>If <var>element</var> is a <code>script</code> element and the <span data-x="duplicate
+    attribute flag">duplicate attribute flag</span> of the token is set, then set
+    <var>element</var>'s <span data-x="concept-script-duplicate-attribute">duplicate attribute</span>
+    flag.</p>
+   </li>
+
    <li>
     <p><span data-x="concept-element-attributes-append">Append</span> each attribute in the given
     token to <var>element</var>.</p>