diff --git a/components/script/dom/characterdata.rs b/components/script/dom/characterdata.rs
index ade189739c3..2d6bfbb706f 100644
--- a/components/script/dom/characterdata.rs
+++ b/components/script/dom/characterdata.rs
@@ -64,6 +64,7 @@ impl CharacterData {
 
     #[inline]
     pub fn append_data(&self, data: &str) {
+        self.queue_mutation_record();
         self.data.borrow_mut().push_str(data);
         self.content_changed();
     }
diff --git a/components/script/dom/mutationobserver.rs b/components/script/dom/mutationobserver.rs
index d0dc201f12e..65f8081c900 100644
--- a/components/script/dom/mutationobserver.rs
+++ b/components/script/dom/mutationobserver.rs
@@ -132,8 +132,8 @@ impl MutationObserver {
                             if *namespace != ns!() {
                                 continue;
                             }
-                            if registered.options.attribute_filter.iter()
-                                .find(|s| &**s == &**name).is_some() {
+                            if !registered.options.attribute_filter.iter()
+                                .any(|s| &**s == &**name) {
                                 continue;
                             }
                         }
@@ -184,7 +184,7 @@ impl MutationObserver {
         }
 
         // Step 4
-        for &(ref observer, ref paired_string) in &interested_observers {
+        for (observer, paired_string) in interested_observers {
             // Steps 4.1-4.7
             let record = match attr_type {
                 Mutation::Attribute { ref name, ref namespace, .. } => {
@@ -193,10 +193,10 @@ impl MutationObserver {
                     } else {
                         None
                     };
-                    MutationRecord::attribute_mutated(target, name, namespace, paired_string.clone())
+                    MutationRecord::attribute_mutated(target, name, namespace, paired_string)
                 },
                 Mutation::CharacterData { .. } => {
-                    MutationRecord::character_data_mutated(target, paired_string.clone())
+                    MutationRecord::character_data_mutated(target, paired_string)
                 }
                 Mutation::ChildList { ref added, ref removed, ref next, ref prev } => {
                     MutationRecord::child_list_mutated(target, *added, *removed, *next, *prev)
diff --git a/tests/wpt/metadata/dom/nodes/MutationObserver-attributes.html.ini b/tests/wpt/metadata/dom/nodes/MutationObserver-attributes.html.ini
deleted file mode 100644
index 3adb1f43ffa..00000000000
--- a/tests/wpt/metadata/dom/nodes/MutationObserver-attributes.html.ini
+++ /dev/null
@@ -1,11 +0,0 @@
-[MutationObserver-attributes.html]
-  type: testharness
-  [attributes/attributeFilter Element.id/Element.className: update mutation]
-    expected: FAIL
-
-  [attributes/attributeFilter Element.id/Element.className: multiple filter update mutation]
-    expected: FAIL
-
-  [attributeFilter alone Element.id/Element.className: multiple filter update mutation]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/dom/nodes/MutationObserver-characterData.html.ini b/tests/wpt/metadata/dom/nodes/MutationObserver-characterData.html.ini
deleted file mode 100644
index 9a4b39b2421..00000000000
--- a/tests/wpt/metadata/dom/nodes/MutationObserver-characterData.html.ini
+++ /dev/null
@@ -1,12 +0,0 @@
-[MutationObserver-characterData.html]
-  type: testharness
-  expected: TIMEOUT
-  [characterData Text.appendData: simple mutation]
-    expected: TIMEOUT
-
-  [characterData Text.appendData: empty string mutation]
-    expected: TIMEOUT
-
-  [characterData Text.appendData: null string mutation]
-    expected: TIMEOUT
-